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The first version of Scientific Rationale (in Turkish) for DAG is prepared elsewhere and now it will only be reached from here for historical purposes.

Scientific Rationale and Drivers (Draft Version - v0.1)

# Topic Assigned to
1.1 Solar System Bodies Sacit, Timur
1.2 Exoplanets Deniz, Aybüke, (Baha/Ralf Neuhaeuser)
2.1 Stars and stellar evolution Ünal, Ayşe, Sacit, Timur
2.2 Transient objects
(SNe, GRBs, SGRs, Novae, Microquasars etc.)
Aysun, Emrah, Eda, Şölen, Ünal, İlham
2.3 ISM and Star Formation Nazım, Umut
Galaxies and Cosmology
3.1 Galaxy Formation and Evolution Aybüke, Eda, Korhan
3.2 Observational Cosmology Aliş, Korhan
3.3 Galaxy Clusters Aliş, Korhan
Synergies with Current and Future Facilities
4.1 High Energy missions
(Gamma-ray and X-ray, Cherenkov)
Tolga, Emrah, Şölen
4.2 Optical Aliş, Korhan, Tolga
4.3 Near-IR Aybüke, Tolga, Sacit
4.4 Mid/Far-IR Umut
4.5 Sub-mm/Radio Umut
Competition in the Northern Sky
5.1 Current and Future Projects with 4m-class Telescopes Korhan, Tolga, Aybüke
5.2 Current and Future Survey Projects Korhan, Tolga, Aybüke

Planets and Stars

Updates: 14.05.2012 (Deniz)

1.2 Exoplanets

Extrasolar planets are systems, which don't belong to the Solar system. There have been total of 765 planets that were detected using different methods (Schneider, J. 2011). Methods used for detections so far are;

  1. Radial Velocity, or Doppler Method (560 planetary systems)
  2. Transits (197 planetary systems)
  3. Astrometry (not a exoplanet discovery but detection of known exoplanets)
  4. Direct Imaging (27 planetary systems)
  5. Microlensing (14 planetary systems)
  6. Timing Variations (12 planetary systems)

So far the astronomical measurement limits are, 0.1–1 ms–1 for radial velocity resolution, few microarcseconds for astrometric measurements, few milliarcseconds for angular resolution, and ~10-10 for the contrast ratio measurements. There are basically three topics to be covered in exoplanet science: 1) Detections, 2) Internal structure characterization, and 3) Atmosphere characterization.

Fig-1.2-1. Schematic showing the rough timeline for milestones for our “3-lanes” of detection, characterization of internal structure (mass, radius, mean density) and the characterization of spectral atmospheres. Near term is approximately 2011-2017, Mid-term 2015-2022, and Long-term beyond 2010. Technological difficulty and time proceeds left to right, and top to bottom (Hatzes, A. P. 2011).

Methods of detecting extrasolar planets

1) Radial Velocity (RV) Method This method is the most common method in finding exoplanets. RV technique provides the mass information of the system and it is also used to check the planet candidates found with transit method. This method will continue to play an important role in exoplanet studies.

Future: Improved wavelength calibration that is needed to achieve an RV error of better than 10 cm s–1, improved instrument stability, and overcoming the intrinsic variability of the star (stellar activity noise).

2) Transit Detection The photometric transit method detects planets by the dimming of stellar light during transit of an orbiting planet through the line-of-sight.

Future:Follow-up observations using high-resolution imaging and photometric observations are needed to confirm the signal on the target star. Medium to large telescopes are finally required to derive the planet mass as well as important fundamental parameters of the host stars.

3) Astrometric Detections In finding extrasolar planets, astrometric detection method is attached with radial-velocity method. By detecting radial component of the radial motion (RV technique) and using astrometry measures mass of the planet can be found without relying on the sin i parameter.

Future: The astrometric detection of Earth analogs requires a precision of better than 1μas, which can be achieved with a space-based interferometer.

4) Imaging Detections Directly detecting such dim objects is one of the hardest things to accomplish. The first successful direct images of extrasolar planets were obtained in 2005 at VLT for GQ Lupi (Neuhäuser et al. 2005) and 2M1207 (Chauvin et al. 2005). Until 2010 it was not possible to detect exoplanets with direct imaging but only under exceptional circumstances. With use of an upgraded system on 1.5-meter portion of the Palomar Observatory's Hale Telescope, 3 known exoplanets orbiting the star HR 8799 was detected (Serabyn et al. 2010).

**Future: Direct imaging campaigns (SPHERE/VLT,EPICS/E-ELT) will complementary astrometric detections. Ground-based direct imaging techniques may have a long enough time base to detect orbital motion of a long-period giant planet and thus to measure its mass. This work can begin with the “Planet Finders” on the 8-m class telescopes and continue with the extremely large telescopes (TMT, E-ELT, GMT).

5) Microlensing "If a foreground object (star, free floating planet, black hole) passes very close to the line of sight to a background star, the 'source', then the gravity of the foreground object acts as a lens. The result, as the projected separation on the sky between source and lens changes, is a characteristically shaped brightening and fading of the source star on a time-scale of a month. If a planet orbits the (not necessarily seen) foreground 'lens' object, its gravity can affect the light rays as well, causing a short deviation from the otherwise symmetric light curve. The duration of these deviations depends upon the mass of the planet - days for a Jupiter mass and hours for an Earth mass" (Hatzes, A. P. 2011). Drawback of this method is that it is hard repeat the observation since alignment needed might never occur again.

Future: Wide-field survey telescopes can be used to provide the high cadence observations needed to detect and follow anomalies. The sensitivity of groundbased microlensing campaigns is governed by angular resolution.

6) Timing Detections It is also possible to detect planetary companions to stars by searching for timing variations. One of the most sensitive techniques in finding planets is the pulsar timing method. By this technique it is possible to detect exoplanets less than a tenth the mass of Earth. Disadvantage of this method is that pulsars are relatively rare. Timing variations of stellar oscillations and also eclipsing binary stars can also be used to search for timing variations in the eclipses caused by planets either around on companion, or circumbinary planets.

Fig-1.2-2. Timeline of current and planned large facilities. Green indicates facilities that are primarily used for exoplanet studies. Not shown are ground-based 8-10m class telescopes. (Hatzes, A. P. 2011).

Exoplanet Studies Road Map

In the study done by Hatzes, A. P. (2011) exoplanet studies were carefully analysed and the road map was proposed. Given in this study the key questions to be answered by this roadmap (in order of difficulty) are;

KQ1: What is the diversity and architecture of exoplanetary systems as a function of stellar parameters and birth environment?
KQ2: What is the diversity of the internal structure of exoplanets?
KQ3: What is the diversity of exoplanetary atmospheres?
KQ4: What is the origin of the diversity and how do planets form?
KQ5: What are the conditions for planet habitability, how common is exo-life and can we detect the biosignatures.

Taking these questions into account, on-going, near (~2011-2017), mid (~2015-2022) and long-term (~2020 and beyond) recommendations for ground and space based observatories can be found in this study.


Chauvin, G. et al. 2005, A&A, 438, L25 ADS
Hatzes, Artie P., 2011, IAUS, 276, 316; ADS
Neuhäuser, R., et al. 2005, A&A, 435, L13 ADS
Schneider, Jean (10 September 2011); Interactive Extra-solar Planets Catalog
Serabyn et al. 2010, SPIE, 7731, 83 ADS

What can be done with DAG

--- Field of view, coating, wavelength coverage (ayni anda ve/veya bulundurmasi gereken filtreler), spectral resolution, spatial resolution, read-out timing (this changes for every instrument), telescope pointing timing (ToO/RRM), tracking precision, MOS/IFU specs. ---

  • Coupled with on going CoRoT, Kepler, and future GAIA results observations to establish stellar properties (mass, radius, abundance, effective temperature), age, level of activity, environment, binarity, number of planetary companions, etc. can be done. High-resolution, high-precision spectroscopy in IR wavelenghts
  • High resolution spectroscopy from ground based observatories in the optical and NIR down to 5 microns. Near IR observations will also be sensitive to dust and possibly clouds in their atmosphere.
  • Radial velocity measurements in infrared for especially young active stars. M dwarf stars are faint and most of their flux is in infrared (IR) region of the spectra. High resolution spectrographs in IR will be required to search for small planets around M dwarfs (precision of 1 m s-1 or better).
  • Broad and narrow-band imagers operating in the Near IR should be used to search for secondary transits of giant planets. Low-resolution IR spectrographs can also be used to search for spectroscopic signatures.
  • Follow-ups for the results of new imaging “planet finder” equipment thats is going to be used in VLT, Gemini and Subaru. Also ground-based spectroscopic follow-up of PLATO transit candidates.
  • Ground-based microlensing searches in IR.


Stars and Galaxies

Updates: 03.05.2012 (Ünal)

2.1 Stars and Stellar Evolution

1. Young Neutron Star Populations

Several young neutron star populations have been identified in the last two decades. These isolated neutron star systems, namely, anomalous X-ray pulsars (AXPs), soft gamma-ray repeaters (SGRs), dim isolated thermal neutron stars (XDINs), rotating radio transients (RRATs), and compact central objects (CCOs) show striking similarities and also rather different peculiarities. For instance, AXPs, SGRs, and XDINs all have spin periods clustered to a narrow range (2–12 s). AXP and SGRs (also known as magnetars) show super-Eddington soft gamma-ray bursts that are not observed from the other populations. In comparison with other systems, XDINs are older (characteristic age ~106 yr) and have lower X-ray luminosities (1030–1032 erg/s) and have not been detected in radio bands. All known XDINs lie within a distance of 500 pc, which indicates that XDINs could have birth rates higher than radio pulsars. RRATs have the unique property of irregular short radio bursts lasting much less than the periods of the sources. Based on the observed number of sources, it was speculated that RRATs could be progenitors of XDINs.

Different evolutionary paths creating different neutron star populations are likely to be due to different initial conditions: magnetic dipole moment, initial spin period and presence or absence (and properties) of fallback disks around the neutron stars (Alpar 2001). Physical properties of these young systems are not clear yet. AXP and SGR bursts require strong (magnetar, >1014 G) fields, nevertheless it is a matter of debate whether these fields are stored in dipole or higher multipole fields of the star. In the magnetar model (Thompson and Duncans 1995), neutron stars in AXP/SGRs are assumed to rotate in vacuum slowing down with magnetic dipole torques. This requires that the magnetar fields should be in the dipole component. This model cannot explain some basic properties of AXP and SGRs, like the period clustering of the sources in 2-12 s range. On the other hand, in the fallback disk model (Chatterjee et al. 2000,Alpar 2001) the strength of the dipole field is required to be <1013 G in order explain rotational, optical, IR and X-ray properties of the sources. In this model, the rotational evolution of the neutron stars are governed by the disk torques acting on the dipole component of the magnetic field.

First evidence for the presence of fallback disk around a young neutron star was found through MIR and NIR observations of AXP 4U 0142+61 (Wang et al. 2006). Most of the other AXP and SGRs were detected in different NIR bands. These sources show variations in X-ray and IR luminosities. Observation of these sources in X-ray enhancement phases in different luminosity regimes are very important to understand the physical mechanisms producing the observed broad data. In FDM, the source of the IR radiation is the irradiated active disk, while in the magnetar model it is attributed to magnetospheric emission from a dipole magnetar field. In the frame of the fallback disk model, it is estimated that not only AXP and SGRs, but also XDINs, possibly RRATs are the sources evolving with fallback disk with conventional magnetic fields. So far, XDINs could not be detected in IR bands. Present upper limits in the IR bands are low and consistent with the expected IR fluxes from these sources. The faintness of XDINs in the IR bands could be explained by their relatively low X-ray luminosities and the corresponding weak X-ray illumination of the disk. Nevertheless, the known XDINs are all at small distances and likely to be the old XDINs. The number of these sources at the ages of AXP and SGRs (~103 – several 104 yrs) are expected to be about an order magnitude higher than that of AXP and SGRs. These younger XDINs, are probably have higher X-ray luminosities and, when identified in X-rays by means of rotational properties, they could also be detected in the NIR and MIR bands.

Among these young neutron star populations, some of them could have evolutionary links and others might completely different evolutionary paths. The aim is to explain the evolution of all these systems including radio pulsars (Çalışkan, Ertan and Alpar 2012) within a unified model with different initial conditions. This could also help in understanding the details of source properties like dipole moments and initial disk masses. It was shown that the general rotational and X-ray properties of AXP and SGRs can be accounted for by the evolution of the neutron stars evolving with fallback disks for certain ranges of initial disk masses and with dipole fields less than 1013 G on the surface of the neutron star (Ertan et al. 2009). A similar work on the evolution of XDINs is in preparation (Ertan et al. 2012). Our model results on the disk properties indicate that a significant fraction of all young neutron star systems, in different evolutionary phases, could be detected in the near and mid IR bands depending on the distances of the souces.

Updates: 13.05.2012 (Mükremin Kılıç)

2. White Dwarfs

A 4m telescope with an infrared imaging camera and Y, J, H, and K filters would be extremely useful for studying white dwarf atmospheres and cosmochronology, their stellar/substellar companions and debris disks.

Atmospheres: Cool M dwarfs, brown dwarfs, and white dwarfs show near-infrared flux deficits due to collision induced absorption (CIA) from molecular hydrogen. Imaging in the near-infrared will provide spectral energy distributions of cool white dwarfs that can be used to constrain the effects of CIA opacity. There are clear problems with the current CIA opacity calculations; observations of a large number of cool WDs in the infrared can help constrain the models for cool WDs.

White dwarf cosmochronology is a powerful method to constrain the ages of the oldest stars in the solar neighborhood, as well as in open and globular clusters, and the Galactic halo. A precise temperature measurement for a white dwarf can be obtained from modeling its optical and infrared energy distribution. This temperature measurement can then be used to estimate the age of a white dwarf, if the distance is known. An infrared camera on a 4m telescope can be used to study a large number of white dwarfs in the Galactic disk and halo to constrain their spectral energy distributions, temperatures, and ages.

Substellar companions: Brown dwarf companions to WDs are important benchmarks for the spectral models for brown dwarfs and massive planets. WDs have well determined cooling ages, which also constrain the ages of their substellar companions. For WDs hotter than 5000 K, Balmer lines are visible in the optical and these lines can be used to estimate Teff and logg for these objects, which give an age estimate. In fact, the first candidate brown dwarf was found around a WD more than two decades ago (Becklin & Zuckerman 1988). Even though only a few more WD + Brown dwarf systems have been discovered since then (Farihi & Christopher 2004; Steele et al. 2009; Day-Jones et al. 2011), the discoveries to date include the coolest known brown dwarf candidate (Luhman et al. 2011, 2012) and brown dwarfs that survived common envelope evolution (Maxted et al. 2006; Debes et al. 2006). New discoveries from a near-infrared imaging campaign on a large number of WDs would have a significant impact on this field and would enable us to calibrate the models for substellar objects.

Debris disks around WDs: Recent discoveries of debris disks around WDs suggest that at least a few per cent of WDs have remnant planetary systems. Since the progenitor main-sequence stars of the WDs in the solar neighborhood range from 1 to 7 Msun, the frequency of disks around WDs can be used to constrain the frequency of planets around intermediate-mass stars. A large near-infrared imaging survey (including the K-band) on a 4m telescope can identify many new WDs with debris disks and constrain the frequency of remnant planetary systems around their progenitor stars. We still do not know if 3-7 Msun stars form planets or not. This could be one way to answer that question.

Updates: 30.09.2012 (Sacit Ozdemir)

3. Eclipsing Binaries

Eclipsing binaries (EB) are composed of gravitationally bound two stellar components which are orbiting around their common center of masses to each other and exhibit eclipses during every orbital period if the inclination angle is fit. Some of them may house more than two componets which are called multiple stellar systems. Owing to mutual eclipces, i.e., transit and occultation events, and radial velocity measurements, the eclipsing binary systems provide much more precise parameters of masses, radius, gravities, densities, etc., than single or non-eclipsing stellar systems. These information are very essential to check the theoretical models on stellar evolution. There are, depending on evolutionary satages, few sub-types of binary systems such as Algol, Beta Lyrae, W UMa, X-ray binaries (XRBs), cataclysmic binaries (CVs).

Updates: 15.10.2012 (Ayse Ulubay Siddiki)

4. Stellar Associations

Stellar associations are groups of loosely bound young stars that share a common origin. They are mostly populated by O and B stars (OB associations), or T-Tauri stars (T-associations). Altough the member stars sparsely fill in the region they occupy, they move with similar velocities. When an association is identified through the common velocities of its stars, it is sometimes called a co-moving group. Since the system as a whole is not gravitationally bound, it is expexted that stellar associations have a relatively short lifetime, after which its stars disperse through the galaxy.

The current effort in the studies of stellar associations can be summarized as follows:

- Identification of new stellar associations

- Studying the early evolution of circumstellar disks at a stage when the planetary systems are believed to form (Gautier et al. 2008)

- Determining the shape of the initial mass function

NOTE: The topics, hence the requirements from DAG, for this subsection mostly overlap with those under subsections 1.2 Exoplanets, and 2.3 ISM and star formation. Please consider to merge this subsection with the ones listed above.

Updates: 01.10.2012 (Sacit Özdemir, Timur Şahin, Yücel Kılıç)

5. Asymptotic Giant Branch (AGB) Stars

The asymptotic giant branch (AGB) stars can be described by evolved low and medium-mass stars which have a central and inert core of carbon and oxygen, a shell of helium burning into carbon, another shell where hydrogen is undergoing fusion forming helium. However, they show spectral composition that is similar to normal stars.

Since AGB stars show large amount of mass ejection, as a result, they are surrounded by a circumstellar (CS) shell of gas and dust. CS shell has an important affect on converting stellar spectrum into a shifted towards infrared wavelengths. This makes IR observations very esential to study the structures of CS shells. In addition, since AGB stars exhibit variability periods up to thousands of days, they should be monitored for long time intervals.


Alpar 2001
Becklin & Zuckerman 1988
Chatterjee et al. 2000
Çalışkan, Ertan and Alpar 2012, in preperation
Day-Jones et al. 2011
Debes et al. 2006
Ertan et al. 2009
Ertan et al. 2012
Farihi & Christopher 2004
Luhman et al. 2011, 2012
Maxted et al. 2006
Steele et al. 2009
Thompson and Duncans 1995
Wang et al. 2006
Gautier,Thomas.N., III; et. al. (2008), ApJ, 683, 813

Updates: 15.10.2012 (Sacit Özdemir, Timur Şahin, Yücel Kılıç, Ayşe Ulubay Sıddıki)

What can be done with DAG

Observational Studies with DAG regarding Young Stellar Associations

Determining stellar membership: Requires the measurement of radial velocities through high resolution (R~30000) spectra.

Circumstellar discs: Determining the properties of the disc requires optical and IR photometry (down to a few microns), as well as high spectral resolution for which the contrast between the star and the planet becomes larger.

• Most of the astronomers and astrophysicists in Turkey have been experienced on eclipsing binaries. Main requirement of these colleagues is to have supplementary radial velocity curves of eclipsing binaries for obtaining a full solution of light curves. Therefore radial velocity curves extracted from either optical or NIR spectra of eclipsing binary systems will largely satisfy the Turkish scientific communitiy.

• Algol type systems have a special importance since they are one of the test laboratory of apsidal motion predicted by the theory of general relativity. Existence of apsidal motion in Algols can be only verified by timing analysis of secondary minima which is difficult to recognize because of the large difference in surface temperatures of the components. However, Planckian energy distribution of the stars offers a chance to have an evident secondary minima. On this occasion, NIR photometry carried out by DAG facilities is going to be useful to determine secondary minima of Algol type systems.

• As the number and sensitivity of high energy experiments in orbit increase, new members of XRBs and CVs, a very small but amazing group of binary stars, are continuously added to the catalogues. Therefore, follow-up observations of such energetic binaries in optical and IR bands will have great impacts on scientific arena.

Observational Studies with DAG regarding AGB and post-AGB stars

In last twenty years, the availability of large IR databases from space-borne telescopes like ISO, IRTS, MSX, SPITZER etc. has substantially improved our knowledge on the AGB stars in general. For instance, their distances are now more reliable than before (see Bergeat & Chevallier 2005 for corrected Hipparcos distances of AGB stars). However, observations from space-borne telescopes in the IR present also disadvantages. In particular, duration of the operational period is quite limited and AGB stars are generally studied with a single-epoch observations (regardless of their variability) therefore our understanding of basic physical parameters is hindered. Solution is ground-based observations at IR wavelengths. Here we list some fundamental topics regarding AGB stars in general and brief information on selected example IR instrumentation.

Mass-loss (efficiency): For mass-loss, its duration and the chemical composition of the matter ejected by is fundamental to understand the AGB phase.

8.5 and 12.5 microns are good indicators, also permits a classification of the chemical properties of the circumstellar envelopes (see also Ciprini & Busso 2003).

Aim: simple relations connecting the strength of the stellar winds to the photometric properties and then to the chemical properties (e.g. enhancement of newly produced carbon and s-elements in the photosphere) of AGB stars.

Extra info.: Photometric observations of AGB stars in mid-infrared, at 10 micron, is important since cool dust normally dominates over the photospheric flux (Corti et al. (2003), Marengo et al. (1999), Busso et al. (1996)).

ISOGal sample, consisting of spectroscopy of 107 candidate AGB stars, could be scrutinized as a start (Schulteis et al. 2003) and sample could be extented to include LMC and SMC AGB stars.

Population synthesis: AGB stars are pulsating variables: one fundamental question awaits for an answer is how their average spectra differ from those of non-variable red-giants and of red supergiants since population synthesis techniques rely on stellar libraries with a broad spectral type and wavelength coverage (for stars of known physical parameters).

Spectral Energy distribution: Necessity for re-analysis of Galactic AGB stars at Infra Red wavelengths to determine their energy distribution, mass losses, and absolute magnitudes (see van Loon et al. 2001, 2005 for planned database).

Example: TIRCAM2 mounted on TIRGO, an italian infrared telescope (locate at 3200m) in Switzerland (Persi et al. 1994). TIRCAM2 consists of five narrow band filters (10% bandwidth) between 8 and 13 m, with the N broadband filter and a circular variable filter having a spectral resolution of 3% in the 8–14 m range.

Near-IR: Cryogenic Array Spectrometer and Imager (CASPIR), a 256x256 InSb detector, mounted on the Australian NationalUniversity 2.3-m telescope, is another example instrument providing direct imaging and spectroscopic capabilities in the 1 – 5 micron wavelength range (Table 1.).

Grism Wavelength range
J 0.99 – 1.32
H 1.50 – 1.81
K 1.98 – 2.47

Table.1 Overview of grisms for CASPIR.

Studying (O-rich) Galactic Bulge AGB stars:

  • Metallicities are in the range -1 < (:cell PQA(PSS(Fe/H):) < 1.
  • They're suitable for follow up observations.
  • They're all oxigen rich with silicate dust features

Measuring Luminosities of AGB stars:

Another problem awaits for a solution for AGB stars is the bolometric variability which can be clearly distinguished in the region of the mid-IR of AGB star spectral energy distributions (observed at different epochs). These kind of observations performed during variability show that period and luminosity is not only shifted at different wavelengths bur also subject to intrinsic variations (possible reason could be a non-thermal energy source). There is still no consensus on the origin of variations in the bolometric magnitudes of the AGB stars.

Photometric Monitoring of AGB stars:

  • As shown by Le Bertre et al (1994), a seperation between C-rich and O-rich AGB stars can be performed on the basis of infrared colour diagrams. By combining near IR observations with mid-IR colours taken from satellite databases (such as IRAS, ISO, SPITZER), much larger samples of sub-types of AGB stars, including also extra-galactic targets, can be studied.
  • In a series of papers, Guandalini et al (2006), Guandalini & Busso (2008) and Guandalini (2010) showed that near to mid infrared colours are crucial to study stellar winds, luminosities and mass loss rates among the sub-types of AGB stars, as M, S, SC, Mira types. Studying such physical parameters seems possible with the IR instrumental facilities of DAG telescope.
  • The AGB stars also include Mira type variables which have pulsation periods of hundreds of days. Phase lags between optical and IR light curves of Miras are very well recognized (see e.g., Price et al. 2010). The Miras as well as other pulsating AGB stars can be photometrically monitored, in both optical and IR regions, to investigate the nature of CS envelope.
  • Asteroseismology is one of the essential tools to investigate stellar interiors. There are some orbiting satellites such as Kepler, CoRoT, etc., to preciselly monitor the possible exoplanet transits. Precise photometric observatins of these missions are very convenient to study stellar pulsations. However, their relatively limited life in orbit, restricted sensitivity interval in wavelength, and finite orientation on the sky all restrict to perform any efficient stellar asteroseismology. The significance of red giants in asteroseismological investigations were emphasized by Christensen-Dalsgaard (2011). The observational instruments of DAG will serve a good opportunity to perform long term monitoring of AGB stars, as well as others, in the context of asteroseismologal studies.


2.2 Transient Objects

Updates: 03.05.2012 (Eda)

GRBs in IR:

GRBs are the most luminous events with 1051-1054 ergs energy release in the universe after the Big Bang. These bursts can be characterized as highly dense "gamma - ray flashes" in the range of a few seconds to several minutes duration.

Although there are successful observations and interpretations of GRBs with multi-wavelength observations, internal and external emission mechanisms still remains unclear with big uncertainties. Scientists are still working to understand the nature of the progenitors of GRBs.

The discovery of GRB afterglows in X-rays (Costa et al. 1997), visible (van Paradijs et al. 1997), and radio (Frail et al 1997) has caused a considerable progress in their understanding, however problems still remains. To solve these problems requires continuous monitoring in X-rays, optical and infrared bands so that the important features of the GRB can be derived. These observations are also give information about distance and locations of GRBs.

Approximately half of GRBs that are well localized by X-ray observations have detected optical or IR afterglows. Photometric and spectroscopic observations of GRB afterglows allow us to determine the redshift of GRBs as well as probe their local environments.

4-m class telescopes can allow for GRB afterglow studies with synergy of the other current and/or planned space and ground based facilities. In this part we summarized relevance of 4-m class IR telescope to Gamma Ray Bursts.

Capable of performing rapid, multi-wavelength observations in X-rays, UV, and optical wavelengths, the Swift satellite plays a vital role in identification of GRB counterparts. Observations of GRB afterglows with IR instruments are required for developing an understanding of the GRB-progenitor circumstellar environment, GRB relativistic outflows, and interaction of the GRB jets with the circumburst medium and the properties of the GRB host galaxies (Greiner & Rau 2011). Note that while Swift has an amazingly fast reaction time, Swift UVOT is only a 0.3 m telescope that cannot observe redward of 6000A. Bigger glass is necessary for the detection and long-term (days to weeks) follow-up of many optical afterglows, which quickly decay past UVOTs sensitivity limits. Additionally, high redshift GRBs have optical afterglows that are suppressed in the optical observer frame due to Lyman-alpha forest absorption. Therefore, IR instruments are required to probe rest frame optical afterglows from GRBs at a redshift >~ 6.

Detection of high-redshift GRBs is particularly important. Up to now four GRBs (GRB 000131 at z~4.5; GRB 050904 at z~6; GRB 080913 at z~6.7; GRB 090423 at z~8.2) have been reported with high redshift with systematic near-infrared observations of GRB afterglows it would be possible to catch high-redshift bursts (Greiner & Rau 2011; Andersen et al 2000; Kwai et al. 2006; Greiner et al 2008; Tanvir et al. 2009). With NIR follow-up, GRBs with potentially extreme redshifts can be identified via IR waveband "dropouts" caused by Lyman-alpha forest hydrogen absorption (see Cucchiara et al. 2011 an example of GRB 090429B at z~9.4). Identifying extremely high-z candidates in rapid photometry allows for more time-intensive spectroscopic observations to be focused only on GRBs that have a high probability of being at extreme redshifts. Such observations are critical for investigations of the early universe, including the epoch of reionization.

The other question in the GRB field is observation of "dark GRBs". Dark bursts afterglows are generally detected in X - rays but have no optical or IR counterparts. Observations of these dark bursts with large ground-based telescopes can increase the possibility of optical/IR afterglow detection. Some dark bursts may not be observed at optical wavelengths because of their high redshifts, a 4-m class infrared telescope would help fill in these gaps. Furthermore, it now appears that many of the dark bursts are dark due to dust absorption in their host galaxies (e.g. Perley et al. 2009 for Visible and IR imaging of Orion Nebula). IR capabilities are crucial for probing GRBs that occur in dusty hosts.

(Acknowledgement: Thanks to Dr. Bethany Cobb for her very useful suggestions)

Updates: 20.11.2012 (Emrah, ilham)

SNe and SNRs in IR:

Supernova Remnant (SNR) studies are important in the theories of interstellar medium (ISM) of matter, and energy into the ISM. However, in spite of the quite large number of Galactic SNRs their observations are impeded by several limitations such as the uncertainty in distances to individual objects and high extinctions along the line of sight in several regions of Galactic plane.

Ground-based and spaced-based observations have allowed many supernova and SNRs in galaxies to be resolved, showing various different morphologies in radio, X-ray, and optical wavelengths. Also with Infrared (IR) observations of supernova and SNRs primarily reveal the thermal continuum emission of shock-heated dust. Although the dust content of SNRs is not directly observable in other wavelength regime, it is possible reveal its fine-structure lines from neutral to moderately ionized species of atoms from carbon to nickel in infrared regime. The distinct advantage of IR observations is that extinction is much lower at IR than optical or UV wavelengths (Arendt et al 1999).

In order to determine the role of SNe in the production of dust in universe the mid-IR observations are critical. Also, the near- and mid-IR observations are useful tools for studying physics of SNRs, such as composition, temperature, distributions and density of the ejecta, radiative shocks of SNRs and shock interactions between SNRs and nearby molecular clouds (Bouchet et al 2006, Lee et al 2011 and reference therein).

Galactic Black Holes in IR

Jet emission from Galactic Black Hole Systems

Radio observations of black holes revealed the presence of jets through their synchrotron emission properties. Technically, having a compact object in a binary system is enough to observe jets, they are observed in neutron star systems (Migliari, S. and Fender, R.P., 2006), even in white dwarfs (Kording, E. et al., 2008). However, the jets from black holes are much more powerful than the jets in neutron stars and white dwarfs. Since the jets observed in Galactic solar mass black holes have similar properties to those observed in AGN, these systems are also called microquasars. Only for a few of microquasars the jets are resolved in radio, and for the majority of the systems the presence of jets are inferred through properties of radio and near infared emission.

Spectral properties of radio emission indicates that there are two types of jets in microquasars. The jets observed during transitions from the hard spectral state to soft or very high state are usually very powerful. These are transient jets and they are so powerful that they could distrupt the inner part of the disk and the corona. For these type of jets, the radio spectrum is a power law with flux decreasing with increasing frequency.

On the other hand, if the radio spectrum is inverted (flux increases, or stays constant with increasing frequency) then the system hosts a compact jet. As the name implies, the compact jets are geometrically small and therefore optically thick close to the black hole. The optically thick part creates the inverted spectrum up to the near infrared band (Blandford, R. D. and Konigl, A., 1979). Sufficiently away from the black hole the jet is optically thin, and the spectral energy distribution (SED) shows a break around the near infrared bands (typically the H band, see Fig. 1.). These jets are only observed in the hard spectral state.

Fig-2.2-1. The origin of emission from black holes.

For some sources it is claimed that the syncrotron radiation from the optically thin part of the jet extends all the way to X-rays and contribute to X-ray emission (Markoff, S. et al., 2001; Markoff, S. and Nowak, M, A., 2004). It was even claimed that the entire X-ray emission from XTE J1550-564 in 2000 at very low X-ray luminosities is originated in the jet (Russell, D. M. et al., 2010).

The jets emit in near-infrared, moreover, the near infrared band corresponds to the break of the SED which provides important information on the size and power of the jet. Therefore microquasars are observed frequently in near-infrared when they are in outburst, especially during the rise and the decay of the outbursts where the system is in the hard state. First detailed investigation of microquasars jets in near infrared was done for XTE J1550-564 (Jain, RAJ, K. et al., 2001), and subsequent work by Homan, J. et al. (2005); Russell, D. M. et al. (2006); Buxton, M., Bailyn, C. D. (2004); Kalemci, E., et al. (2005) detailed information about the relation between near infrared emission, jets and X-ray spectral and temporal properties. As seen in Fig. 1, the near infrared can be originated in the jet, but there can also be contributions from the secondary star and outer parts of the accretion disk. Therefore detailed investigation of light curves in near infrared, optical and X-rays (Buxton, M. et al., 2012) as well as SEDs must be done to fully account for each component (Dincer, T. et al., 2012).

Finally, there is a correlation between the near infrared flux and X-ray flux in these sources (Corbel, S., et al., 2000; Russell, D. M. et al., 2006; Coriat, M., et al., 2009). This correlation may mean a common emission mechanism (synchrotron), but it may also mean a common reservoir for the accretion and ejection. There is another mechanism that relates X-rays to jet launch: synchrotron self Compton (SSC). In SSC, the synchrotron radiation created in the jet is Compton upscattered by the electrons that create the synchrotron radiation. In this case the origin of soft photons that are upscattered and created the variability in these system may originate in the jet (Markoff, S., et al., 2003).

In the mid-infrared band usually satellites are required to conduct observations and this reduces the number of studies on microquasars in mid-infrared. An important study at mid infrared was done by Migliari, S., et al. (2007) using VLA in radio, SPITZER in mid infrared, SMARTS in near infrared and optical and RXTE for X-rays. This work showed that for GRO J1655-40 synchrotron+SSC can explain the entire SED in the hard state. A recent work by Gandhi, P. et al. (2011) used WISE data to constrain the break frequency in the infrared. But both cases utilized single pointed observations, and could not take into account day to day variability and could not constrain the properties of jet launch.

X-ray timing studies to understand the relation between power spectra and jet launch

For XTE J1550-564 and XTE J1752-223 it was claimed that direct synchrotron emission dominates the X-ray emission in the hard state at low luminosities. If this is the case there should be a manifestation of this change in X-ray timing properties. Tolga Dinçer and Emrah Kalemci have been investigating this for many microquasars for which there is good coverage in near infrared that lets determining the time of jet launch. In Fig. 2. an example sequence of power spextra is shown for XTE J1550-564. The sequence shows that there is no drastic change in the power spectra as the jet turns on, however the disappearance of the quasi-periodic oscillation is interesting

Fig-2.2-2. XTE J1550-564 2000 outburst decay, evolution of power spectra and the near infrared flux indicating jet launch. Turqoise circles are near infrared background, and the purple circles are the near infrared fluxes on top of the background.
Fast timing studies in optical and infrared

Two very important fast timing studies in optical and infrared were done for the microquasar GX 339-4. In both studies ms scale timing in optical (Gandhi, P. et al., 2008) and infrared (Casella, P. et al., 2010) data were used to create power spectra and compared to simultaneous X-ray power spectra using RXTE. In the hard state the infrared and the X-ray power spectra are very similar (see Fig. 3). With ms capability it is also possible to do autocorrelation studies. This kind of studies require large infrared telescopes with appropriate CCDs or special instruments and software pipeline to analyze the data.

Fig-2.2-3. Left: Simultaneous X-ray-K band light curve of microquasar GX 339-4 taken with VLT. Right: Power spectra from these light curves. Both from Casella, P. et al., 2010].
Jet launch timescale

The jet signatures in the near infrared are always observed a few weeks after transition in X-ray timing (Kalemci, E., et al., 2005; Kalemci, E., et al., 2006), when the X-ray spectra are hardest and the disk flux is less than 1% of the total X-ray flux in 3-25 keV band. This is shown in Fig-2.2-4.

The jet formation timescale is probably related to formation of corona[33]. The formation of the corona may also be important in terms of carrying magnetic flux inwards for jet launch (Beckwith, K et al., 2009).

Microquasars and DAG

Most microquasars are transient systems and the jets are observed during hard X-ray spectral states. This means that infrared observations must be target of opportunity, and must be coordinated with X-ray and radio facilities. Even though this places a strain on telescope scheduling, it is a well established fact that the true nature of astrophysical sources are often investigated only with multi-wavelength observations.

To track all state transitions and to obtain jet reactivation time the near infrared and optical observations must be conducted daily after the X-ray spectral hardness is confirmed. The photometric observations in J, H, K, I, B, V should be conducted for 10 to 20 days to evaluate the entire evolution.

It is unfortunate that most of the microquasars can only be observed from the South Hemisphere, on the other hand for a handful of systems DAG would be suitably located, especially during summer.

It is absolutely essential to have CCDs, or special readout systems for fast timing. The size of the DAG would be enough for bright systems. Especially if LOFT is selected for the next medium size explorer at ESA, simultaneous observations with LOFT and DAG would be very beneficial. Without LOFT it may be possible to use Indian ASTROSAT for fast timing in X-rays along with DAG.

Fig-2.2-4. The evolution of X-ray spectral index (black), near infrared fluxes (red) and radio (blue).

Updates: 03.05.2012 (Şölen)

Cataclysmic Variables (Novae, Dwarf Novae, Magnetic CVs)

Cataclysmic variables (CVs) are compact binaries hosting a white dwarf (WD) primary star accreting material from the Hydrogen rich companion. The accretion occurs through an accretion disc in cases where magnetic field of the WD is weak (B< 0.01 MG) and such systems are referred as nonmagnetic CVs.

Classical Novae and Ground-based IR Observations

A subset of Cataclysmic Variable systems gives rise to classical/recurrent novae (CNe/RNe) in which an outburst on the surface of the white dwarf is due to a thermonuclear runaway (TNR) in the accreted material and results in the ejection of about 10$-4-10-7 solar masses of material at several thousand kilometers per second (Warner 1995, Starrfield 2001, Bode & Evans 2008, Balman 2012). RNe repeat their outbursts with a cycle of few tens of years. CNe/RNe are the third most violent of the stellar explosions that can occur in a galaxy after Gamma-ray bursts and Supernovae. CNe/RNe also participate in the cycle of Galactic chemical evolution by ejecting grains and metal enriched gas as a source of heavy elements for the interstellar medium (Gehrz et al. 1998). CNe/RNe are related to Supersoft X-ray sources (SSS) which are the probable progenitors of SN Ia explosions.

During a CN outburst the stellar remnant and the ejecta can be probed in NIR and Mid-IR wavelengths. A quasi-photospheric stellar spectrum with weak atomic lines and some P-Cygni profiles changes to one showing a wide range of deep absorption features indicating a cool extended atmosphere (H2O, CO, AlO, SiO, TiO, SO2, OH, SH, Si) with possible circumstellar dust shell (Lynch et al. 2004, Evans et al. 2007). Following a classical/recurrent nova eruption as the early phases subsides the ejecta/shell will start to show IR emission lines. The ejecta is then believed to be synthesizing molecular grains and dust. Eventually, as the central WD enter UV and the X-ray rejime, the ejecta goes into nebular and coronal line emission phase where one finds hydrogen recombination lines, free-free continuum and IR coronal lines. One can use CLOUDY software to physically interpret the IR data (Hayward et al. 1996, Evans et al. 2007a, Lynch et al. 2008). In this way, we can study the spectroscopy of the ejecta, its elemental abundances, dust grain minerology, dust formation and dust distruption. Using spectroscopy we can model the inhomogeneous dust shell and the interaction of this shell with the interstellar medium (Lynch et al. 2004).

Magnetic CV Studies

The magnetic CVs (mCVs) constitute about 25% of the entire population of CVs. It has two subclasses depending on magnetic field strength. Polars (AM Her type systems) have B>10 MG where this strong field causes the accretion flow to directly channel onto the magnetic pole of the WD inhibiting the creation of an accretion disk (see Cropper 2002; Warner 1995). Polars show strong circular an linear polarization modulated at Porb and the WD rotation Pspin is synchronized with the binary orbit. Only about 1% of the Polars are found to show asynchronicity. The second class of mCVs are Intermediate Polars (DQ Her type systems) that have less field strength compared with Polars of about 1-10 MG. In this case, the accretion takes place via a truncated disk to the magnetic poles through accretion curtains. Near the surface of the WD, the accreting material forms a strong shock where the post shock region heats up to 10-20 keV and then cools via thermal Bremsstrahlung (Patterson 1994; Hellier 1996; de Martino et al. 2008; Brunschweiger et al. 2009). IPs are asynchronous systems where orbital period of the system Porb is larger than the spin period of the white dwarf P$_{\rm{spin}}$. Majority of the IPs have Pspin/Porb <0.1, theoretically in the 0.01-0.6 range (Norton, Wynn & Somerscales 2004; Norton et al. 2008; Scaringi et al. 2010).

In magnetic cataclysmic variables the material that has channeled onto the field lines will emit cyclotron radiation as it spirals in. This emission will reveal itself as humps in the spectra and one calculate the magnetic fields of CVs in such systems. If the field strength is B<40 MG all magnetic WDs will emit cyclotron radiation in the IR rejime, this includes low field Polars and Intermediate polar systems (Schwope, Schwartz, Greiner, 1999, Johnson, J.J. 2005).

General Comments

IR rejime is one of the most important bands where the outer accretion disk is studied in CVs (largely-time variability).

As part of Cataclysmic Variable studies, in Classical Nova outbursts, Intermediate Polars and Polars, polarization studies can be conducted in IR wavelenths. In CN polarization occurs due to electron scattering, polarization in resonance lines or Mie scattering from dust grains in the IR (Evans et al. 2002). We can study the geometry of the ejected nova shell using polarization (see IR polarization applications Jones, T.J. 2011).

In Mid IR wavelenths SPITZER telescope has been able identify excretion disks of dust outside the Cataclysmic Binaries and hot WDs. SPITZER has identified this excess emission on top of the binary/star emssion in the IR and the accretion disk component. It is possible to try to disentengle dust disks and study them in the NIR and Mid-IR with longer exposures using a ground-based observatory (Brinkworth et al. 2012, 2009, Hoard et al. 2009, 2007).

Updates: 15.10.2012 (İlham, Aysun, Eda)

Ultraluminous X-ray Sources (ULXs)

Ultraluminous X-ray sources are the brightest extragalactic X-ray point sources located away from the nucleus of their host galaxy. It is widely believed that ULXs are formed from some extreme structure of accreting X-ray binary containing a black hole. Their X-ray luminosities greatly exceed the Eddington luminosity (LEd) for a 20 M black hole. They are characterized by extremely high luminosities in the range of 1039-1042 erg s-1 (Colbert & Mushotzky 1999, Makishima et al. 2000). These high luminosities could be as a result of accreting rates onto intermediate-mass black holes (IMBHs) with masses ~102-104 M if they radiate isotropically at sub-Eddington levels (0.01-0.1 of LEd) as observed in stellar black holes (Colbert & Mushotzky, 1999). The high luminosity may also be explained by particular radiation mechanisms from accretion either onto normal stellar-mass black holes (~10 M) with strong beaming effects (King et al. 2001) or massive stellar black holes (≤ 100 M) with super-Eddington emission (Begelman 2002). ULXs are ideal targets to study accretion physics under extreme conditions, and to search for IMBHs which are important to investigate stellar evolution and formation of super massive black holes (Feng & Soria 2011).

The nature of ULXs is still uncertain. Therefore, multiwavelength observations with ground- and space-based telescopes are valuable tool to understand physics and nature of the ULXs. These observations are also important to compare characteristics of ULXs with active galactic nucleus (AGN) and Galactic stellar-mass black holes. Radio observations could give important hint about their geometry, energetics, and lifetime (Miller et al. 2005). Optical/infrared observations are considerable to study the properties of putative ULX binary systems, and these observations also provide relatively direct indications of their masses of the components. For example, a sample of ULXs are associated with extended optical emission nebulae which often show both low and high ionization emission lines. The morphologies and emission line fluxes of these nebulae could then be used to investigate properties of the emitting gas, which provides important information (such as the intrinsic luminosity) about the energizing source (Pakull & Mirioni 2002, Russell et al 2011 and reference therein).

The high-excitation lines observed in nebulae, such as the optical HII recombination line (λ=4686) used to characterize the the intrinsic X-ray luminosites of the ULX (Kaaret et al 2004). Similar work have been done in the infrared band, where some contributions found by the ULX to the emission lines like (:cell PQA(PSS(SiII):) 34.82μm, (:cell PQA(PSS(SIII):) 33.48μm, (:cell PQA(PSS(OIV):) 25.89μm, (:cell PQA(PSS(NeV):) 24.32μm, and (:cell PQA(PSS(NeIII):) 15.56 μm. Especially the infrared (:cell PQA(PSS(OIV):) emission line (together with (:cell PQA(PSS(NeV):)) is a well-established signature of high excitation, usually associated with actively accreting black holes and active galactic nuclei. These high ionization lines used to constrain the Spectral Energy Distribution (SED) of the ULX and its companion. The photoionization modelling of the infrared lines of the ULXs can also be perform to constrain the bolometric luminosity of the ULX and for better understanding the morphology and origin of the emission lines in some starbust systems containing black hole binaries (Berghea et al 2010a, 2010b).

Optical observations showed that ULXs have point-like counterparts with correspond to early-type donors. However, the optical emission from the counterpart may have a strong contribution from the accretion disk (direct and irradiated). This could make it harder to determine the mass and spectral type of the donor star from the luminosity and colors of the optical counterpart. Therefore, obtaining a full SED of the ULX from the far-UV to the near-infrared could be helpful in order to separate the contributions coming from the accretion disk versus the donor star (Feng & Soria 2011, Grise et al. 2012).


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Updates: 20.11.2012 (Emrah, Şölen, Aybüke, İlham)

What can be done with DAG

DAG could be utilized along with X-ray and radio faicilities to conduct target of opportunity observations of galactic black hole transients with jets. Close to jet formation (confirmed by X-ray analysis), photometric observations in J, H, K, I, B, V should be conducted for 10 to 20 days to evaluate the entire evolution. Having a 4-4.5 m telescope has its advantages for faint sources and sources in crowded areas. It would fare much better than current telescopes like SMARTS in terms of such sources.

It is absolutely essential to have CCDs, or special readout systems for fast timing. The size of the DAG would be enough for relatively bright systems. Especially if LOFT is selected for the next medium size explorer at ESA, simultaneous observations with LOFT and DAG would be very beneficial. Without LOFT it may be possible to use Indian ASTROSAT for fast timing in X-rays along with DAG. The only example we have for such studies in done by Casella et al. at VLT with 8m telescope. The time resolution of 60ms was more than enough to do simultaneous timing observations in the low hard state. For very bright sources going down in time resolution may result in observations at the beginning of hard state or in the very high state in which the variability is faster.

If DAG is extended to mid-infrared, it will be possible to characterize the break in the jet SED much better. The WISE data for GX 339-4 indicates that the break may be at mid-infrared for the rise hard state.

In order to conduct the Cataclysmic Variables reserach in IR the 3.5-4 m size of the telescope should suffice. The CCDs should have high QE and sensitivity. A good echelle and high and low resolution providing spectrograph is also essential. High time resolution for fast timing will be important to study the outer disk and eclipse studies in CVs to derive structure of the outer disk or the accretion shock at the poles but should be done with a different CCD then the main CCD. An instrument to conduct polarimetry should be optimized (see Jones 2011)

Rapid follow-up of GRBs in the near-IR is essential in order to detect and localise both the high-redshift candidates and "dark" GRBs. An instrument covering an optical and all near-IR bands at the same time (i.e. GROND for imaging or XSHOOTER for spectroscopy) is ideal as it will help avoiding the complication due to the shape of the light-curve of the GRB afterglows.

To search SNe, SNRs and ULXs in near and mid -infrared region could be possible with ~4m telescope and high resolution spectrograph. The near- and mid-IR emission lines ((:cell PQA(PSS(Fe II):), H 2, etc.) are useful tools for studying evolution of SNRs and determining role of SNe in the production of dust in universe. Observing high-excitation lines spectrally and obtaining a full SED of the ULX in infrared could be helpful to separate the contributions coming from the accretion disk versus the donor star in the ULX systems.


Updates: 04.05.2012 (Nazım)

2.3 ISM and Star Formation

Planetary Nebulae (PNe)

A planetary nebula (PN) is an emission nebula consisting of an expanding glowing shell of ionized gas ejected during the asymptotic giant branch phase of certain types of stars late in their life. Planetary nebulae are amongst the most photogenic and complex of celestial phenomena but are also amongst the most important to properly understand. They are important probes of nucleosynthesis processes, mass-loss physics and Galactic abundance gradients, and, because their progenitor stars dominate all stars above one solar mass, PN are responsible for a large fraction of the chemical enrichment of the interstellar medium, including the seeding of pre-biotic carbon between the stars.

Furthermore, their rich emission-line spectra enable detection to large distances. These emission lines allow the determination and analysis of chemical abundances and permit the estimation of shell expansion velocities and ages, and so probe the physics and timescales of stellar mass loss (e.g. Iben 1995). The measured radial velocities can trace the kinematic properties of observed PN, enabling us to decide if they belong to a relatively young or old stellar population. The kinematic properties of PN in galaxy halos also give strong constraints both on the mass distributions and formation processes of giant elliptical galaxies (e.g. Bekki & Peng 2006; |Douglas et al. 2007), making them useful kinematical probes for understanding the structure of galaxies, and to test whether a galaxy contains a substantial amount of dark matter (e.g. Romanowsky et al. 2003; Herrmann & Ciardullo 2009).

There are roughly 3,000 planetary nebulae known (Kohoutek, 2001:1500 PNe, Acker et al., 1992:1143 PNe) in the Milky Way Galaxy and surveys continue to find more.

PN Surveys:

  • Southern Sky:
    • The AAO/UKST Supercosmos H-alpha Survey (SHS):
      UKST Telescope (1.2 m, FOV:6ox6o)
    • The Macquarie/AAO/Strasbourg H-alpha Planetary Galactic Catalog (MASH):
      UKST Telescope (1.2 m, FOV:6ox6o)
      Technique: difference imaging; H-alpha + (:cell PQA(PSS(NII):) 6548, 6584A
  • Northern Sky:
    • The INT/WFC Photometric H-alpha Survey of the Northern Galactic Plane (IPHAS):
      Isaac Newton Telescope (INT, 2.5m)
      Technique: difference imaging; H-alpha, r and i filters

The availability of wide-field imaging surveys of high resolution and sensitivity across di erent wavelength regimes in the optical, MIR and radio in particular, not only provide new discovery media but also give enhanced opportunities to explore the broader multi-wavelength properties of PN and their mimics than hitherto possible (e.g. Parker et al. 2006; Cohen et al. 2007).

HII Regions

An HII region is a large, low-density cloud of partially ionized gas in which star formation has recently taken place.

Much of our current knowledge regarding star-forming patterns and circumstellar disk evolution derives from the study of molecular cloud complexes within a few hundred parsecs of the Sun. Among these are a large number of lower mass clouds such as Taurus and, more infrequently, dense clouds like Orion, which is the prototypical high-mass and high-density star-forming region. While nearby cloud complexes serve as our primary empirical guide to understanding the formation and early evolution of stars, it is important that we study more than just the nearest examples.

The physical appearance of the nebulae on optical images is thought to reflect a combination of a large, background HII regions overlaid by several foreground, dark clouds, with the edges of the dark clouds illuminated by the optically unseen primary exciting star of the HII region.

Fig-2.3-1. (Left) Optical and (Right) near-IR image of some portion of the Orion Nebula.
Image credit: NASA, STScI, ESA.

Updates: 09.05.2012 (Umut)

Star Formation

Stars like our Sun form deep inside molecular clouds. At the very outset of star formation, in order for a star to condense material; the force of gravity (which tends to contract material) must overcome the thermal pressure (which opposely push the interstellar material apart). This material therefore starts to accrete onto a dense center. According to the gas law, the lower pressure regions must be the regions that are as cold as possible. The only regions in the Interstellar Medium to have dense and cold conditions to ignite star formation are the cold and dark molecular clouds. A typical cloud core has a density of n~104 cm-3 and a temperature of T~10K. Once the cloud start to collapse into its own gravity, it begins to produce stellar luminosities, at which point the protostellar phase begins. Star formation is a multi-step process from prestellar core to planet forming disk where it is evolved in time.

With the recent mid-infrared Spitzer and Gould Belt surveys, confirmed number of young stellar objects (YSOs) have increased significantly in the recent years (e.g., Evans et al., 2009; Rebull et al., 2011). Among those, low-mass young stellar objects have traditionally been classified based on their observed infrared (IR) slope, in the wavelength range from 2 to 20 µm (Lada & Wilking, 1984) or their bolometric temperature, Tbol (Myers & Ladd, 1993). In the earliest stages of star formation, most of the emission appears at far-IR and submillimeter wavelengths. In the Class 0 stage (André et al. 2000), which is the earliest and deeply-embedded stage of YSOs, the protostar is surrounded by a collapsing envelope and a circumstellar disk through which material is accreted onto the growing star (Menv >> M). This stage lasts only a short time, typically ~104 – 105 yr, but it is critical for the subsequent evolution since the mass of the star and the physical and chemical structure of the circumstellar disk are determined here. These protostars also power bipolar outflows with extreme characteristics such as a very high degree of collimation and evidence for shock processing of molecular gas even in cases of very low stellar luminosity (Tafalla et al. 2000). In the subsequent Class I phase, lasting a few ~105 yr, the envelope is dispersed by the outflow, the disk grows, the YSO becomes brighter at IR wavelengths and the outflows diminish in power. The radiative transfer of those protostars are mainly determined by the dust in the envelope therefore rich molecular lines are seen in the IR to sub-/mm wavelengths.

In the later phases of star formation a.k.a. T-Tauri phase is one of the groups of pre-main sequence objects where shows protoplanetary disks. Since the surrounding dusty envelope more and more disappeared in this later phase, the central source start to be visible. However, the temperatures are still well below normal stellar temperatures, so most of the radiation is given off in the infrared and yet cannot be observed with the optical instruments. These sources are also showing irregular variablities which creates a lot of interest.

Size also does matter. Comparing with the total lifetimes of a star, the protostellar phase of a low-mass star is (105-7 yr) quite short so that the IR phase is much shorter than the entire lifetime of 109-10 yrs (as seen in optical). However, in high-mass sources, the star spends almost its entire lifetime as cool infrared objects. Specifically, the duration of protostellar phase in high-mass sources are too short comparing with the low-mass counterparts which makes less number of known sample for high-mass sources. Therefore IR surveys are more valid to find and study these objects.

The still valid questions are;

  • What type of clouds or locations within a cloud are best sites for star formation and eventually form a star?
  • What is the star formation efficiency?
  • What is the initial mass function?
  • What is the difference/link between the low- to high-mass star formation?
  • What is the nature of FU Orionis phenomenon? (Hartmann & Kenyon, 1996)


Acker et al., 1992
André et al. 2000, in Protostars & Planets IV
Bekki & Peng 2006
Cohen et al. 2007
Douglas et al. 2007
Evans et al. 2009, ApJS, 181, 321
Hartmann & Kenyon, 1996, AnuRev, 34, 207
Herrmann & Ciardullo 2009
Iben 1995
Kohoutek, 2001
Lada & Wilking, 1984, ApJ, 287, 610
Myers & Ladd 1993, ApJ, 413 L47
Parker et al. 2006
Rebull et al. 2011, ApJS, 196, 4
Romanowsky et al. 2003
Tafalla et al. 2000, A&A, 359, 967

Updates: 13.05.2012 (Selçuk Topal)

Molecular gas and star formation

Almost 40 years ago, interstellar medium (ISM) was thought to be atomic and the molecules were thought as trace abundance. However, after detecting some dominant molecules apart from H2 for the first time, such as CO (Wilson et al. 1970; Penzias et al. 1970; Solomon et al. 1971) the second most abundant molecule in ISM, we realised that the ISM is not only atomic, but also molecular.

How do the molecules form? You cannot simply combine two atoms in the ISM to create a molecule. Because the problem is that it takes more than Hubble time, so more than the age of the universe. So, there must be a 'faster' way to create molecules. The binding energy between the interacting atoms should be carried away by sort of mechanism that molecule can form. The dust grain can do it on their surface. Hydrogen atoms hit the dust, combine with another atom and hydrogen molecules are created. The binding energy is absorbed on the surface of the dust grains. Ones hydrogen molecules form, other more complex molecules can be created relatively easily by hydrogen molecule interacting with other atoms in the ISM. The dust has a crucial role in forming hydrogen molecules and so, the other molecules and finally forming stars and planets that we see today. We now know that ISM hosts atomic, molecular and dusty environment requiring to be probed in UV, visual, IR and radio wavelengths.

Molecules are located deep down the clouds where the density and temperature high enough. Since the light coming from the centre of the cloud will be absorbed by the dust, it is impossible to see behind the dust in optical wavelength. Only the radio emission can pass the dust easily. Molecules cool the clouds by emitting photons, and clouds start to collapse that allows to create necessary physical conditions, such as high gas pressure leading higher temperature, at the core of clouds to form stars. Stars deep inside the cloud heat the gas and dust around, and the dust starts to shine in infrared wavelengths. This is why, not only sub-mm or mm observations, but also infrared observations are complementary tools to get better understanding of star formation occurring in the molecular ISM.

Today infrared observations are used to study on polycyclic hydrocarbon (PAH) molecules in mid-infrared as a star formation rate indicator (Calzetti, 2011), to derive molecular mass through the direct detection of mid-IR H2 emission which is done indirectly in radio using CO emission (Peterson et al. 2012).


Calzetti D., 2011, EAS, 46, 133
Penzias A. A., Jefferts K. B., & Wilson R. W., 1970, AJ, 165, 229
Peterson B. W., et al., 2012, ApJ, 751, 11
Solomon P., Jefferts K. B., Penzias A. A., & Wilson R. W., 1971, AJ, 163, L53
Wilson R. W., Jefferts K. B., & Penzias A. A., 1970, AJ, 161, L43

What can be done with DAG
  • Star formation is still mystery. Specifically T-tauri phase can be very well studied with DAG. Also binary stars has a great expertise in Turkey, however, binary star formation is simply a huge gap in knowledge. Specifically late stages of star-formation is best observed with the IR instruments and combing the expertise with the IR observations of these sources may help understanding the formation.
  • PN surveys requires big FOV (greater than 1 degree) and high pixel scale (less than 1 arcsec).
  • Spectral confirmation of found PNe is needed in optical band with a medium (10000) or high resolution spectrometer (100000 to measure radial velocity in 1 km/s).


Galaxies and Cosmology

Updates: 14.05.2012 (Aybüke)

3.1 Galaxy Formation and Evolution

There are still many open questions in the astrophysical history of the Universe, in the context of galaxy formation and evolution and the era of re-ionisation:

Galaxy Formation and Evolution

  • What was the nature of the first stars?
  • When did the first galaxies assemble and what were their properties?
  • What kinds of stars are galaxies made of?
  • How many generations of stars do galaxies host and when did they form?
  • What is the star formation history of the Universe?
  • When and how did galaxies as we see them today form?
  • How did galaxies evolve through time?

The Era of Re-ionisation

  • When did it happen?
  • What caused it (stars, galaxies, ...)?


There are different methods of observations to look for the answers of the open questions above:

  • large area surveys to study the galaxy formation and evolution and to look for rare objects like very high-redshift quasars or brown dwarfs,
  • deep surveys to study the first galaxies and the faint end of the galaxy population,
  • multi-band imaging in NIR or NIR spectroscopy to study the first galaxies/stars and the era of re-ionisation,
  • narrow-band designated redshift surveys,
  • follow-up observations of Gamma-ray Bursts (GRBs) to locate and study the host galaxies and probe the otherwise undetected galaxy populations and high-redshift galaxies

Current examples in the near-IR:
VISTA surveys like UltraVISTA, VIDEO, VHS, VIKING; UKIDSS surveys like LAS, DXS, UDS

High-redshift galaxy observations are essential for these two fundamental astrophysics subjects: galaxy formation and evolution, and the physics of the early Universe.

Updates: 14.05.2012 (Ayse, Tolga)


The innermost regions of some galaxies output high amounts of energy. These objects are classified as active galactic nuclei (AGN). The activity is believed to result from the infall of material onto the central supermassive black hole via a sub-pc scale accretion disc. The observations of AGN at infrared wavelengths can be aimed at:

  • Identification of AGN among normal galaxies by looking for a power-law in the spectrum (Stern et. al. 2005)
  • Understanding the nature of the pc-sized dusty torus which is believed to play a key role in AGN classification (Elitzur & Shlosman 1988)
  • The AGN-starburst connection


Elitzur, M. and Shlosman, I., ApJL, 648, 101, (2006).
Stern et. al., ApJ, 631, 163, (2005).

What can be done with DAG

Thanks to the nuStar and Spectrum-Roentgen Gamma satellites and continuous FERMI monitoring, when DAG is established there will be thousands of newly discovered AGN.

DAG can contribute to observations of these sources in a number of ways.

  • Multiwavelength imaging : Thanks to the planned two Nasmyth foci, DAG can perform quasi-simultaneous optical - NIR imaging of a number selected AGN. Such observations, when combined with high (X-rays to TeV) and low (mm - radio) energy data may help revealing the nature of the accretion and structure of the jet in these systems. For such a purpose only two standard imagers with high QE in optical and NIR can be enough. Since the variability timescales are long in these systems timing resolution is not important. Due to the improved spatial resolution of high energy instruments, coordinates of newly discovered sources will be accurate enough. Therefore the field of view of the imagers is not really important for these observations (field of view of several arcminutes should be enough to have a comparison star fit in the image).
  • Spectroscopy : First of all will be necessary for the determination of the redshift of a newly discovered AGN. Also can be used in long term monitoring programs to obtain information on the time evolution specific line features. For this purpose a TFOSC or EFOSC type high S/N instrument would be enough with relatively moderate resolution.
  • Polarization measurements : For relatively brighter AGNs (they are typically bright enough) polarization measurements obtained at several bands and the time evolution of these measurements may provide important knowledge about the nature of the relativistic jet when combined especially with Gamma-ray flux variations.

All of the above mentioned methods generally need relatively long observation campaigns that last several years, where individual observations are obtained with a frequency of maybe 1 or 2 per night per source. This requires an observatory policy that allows obtaining regular monitoring observations of selected sources during a given night although the night was given to a different project. Since the individual AGN observations will be short it should not be a problem for the observer but this needs to be planned and organized in advance. Also at robotic observations (at least to some degree) will be very important for these regular monitoring observations.

Also monitoring of a number of AGN with high energy telescopes open the chance for a number of ToO observations in the optical and NIR. DAG observatory policy should also be designed to allow these kinds of ToO observations.

Finally a lot of AGN that will be discovered in the future will be highly obscured. Therefore opposite to the existing population of currently known AGN, these systems will be significantly dimmer. So these newly discovered sources will often be more suitable targets for DAG instead of smaller telescopes that are usually used these days.

Updates: 14.05.2012 (Korhan)

Lyman break galaxies (LBGs)

Lyman break galaxies facilitated for the first time observational estimates of the star-formation history of the Universe out to high redshifts (Madau et al. 1996; Steidel et al. 1999). Lyman-break galaxies are star-forming galaxies at high redshift that are selected using the differing appearance of the galaxy in several imaging filters due to the position of the Lyman limit. These star-forming galaxies at redshifts z>2.5 will be very faint or absent in the U-filter since for z>2.5 this filter is sensitive to flux from the blue side of the Lyman-limit in the restframe of the galaxy. Lyman-limit shifts to greater wavelenghts due to the expansion of the universe. LBGs can be selected from deep broad-band photometry using the Lyman-break, or "dropout", technique pioneered by Steidel, Pettini & Hamilton (1995). The technique has primarily been used to select galaxies at redshifts of z = 3–4 using ultraviolet and optical filters, but progress in infrared astronomy has allowed the use of this technique at higher redshifts using infrared filters (Curtis-Lake et al. 2012; Bielby et al. 2012).

Fig-3.1-1: A new technique (Lyman-Break technique), in combination with the powerful light--gathering power of the new generation of ground--based optical/infrared telescopes, is allowing one to map out the structure traced by galaxies on large scales, when the universe was only 10% of its current age.The images were taken through red, green, and ultraviolet filters specially designed for finding high redshift galaxies. The object at the center of the circle is clearly present in both the red and the green image, but disappears in the UV image.

Updates: 14.05.2012 (Aybüke)

Dedicated Projects/Examples

Spectrographic Areal Unit for Research on Optical Nebulae - SAURON
SAURON is a panoramic integral-field spectrograph using a lenslet array based on the TIGER principle (Bacon et al. 1995). SAURON uses a lens array to obtain two-dimensional spectroscopy with complete spatial coverage over a field of 33″x41″ in low-resolution mode (0.94" lenslets) and of 9″x11″ in high-resolution mode (0.26″ lenslets). The spectra cover 4800 Å to 5400 Å with a resolution of 3 Å (σ=75 km/s). It is a dedicated instrument that was mounted on the 4.2-metre William Herschel Telescope (WHT) on La Palma. It was used to measure the kinematics and line strength distribution for a representative sample of 72 nearby early-type galaxies (ellipticals, lenticulars, and Sa bulges, in clusters and in the field). The main goal is to understand the formation and evolution of elliptical and lenticular galaxies and of spiral bulges from 3D observations.
Near-infrared diagnosis of stellar populations
Near-IR would provide an excellent opportunity to conduct studies like SAURON without being effected by dust obscuration. The NIR data is very valuable source of information both for obscured galaxies like starbursts and for early type galaxies whose NIR rest-frame light is dominated by a single component of the stellar population: cool giant stars. Moreover, the NIR colours and indices are more nearly mass-weighted, i.e. the NIR mass-to-light ratio is closer to one (e.g. Worthey 1994, ApJS, 95, 107). Recent studies have shown that the NIR diagnostic of stellar populations is a powerful tool in braking some of the current diagnostic degeneracies, when coupled with novel stellar population models (e.g. Maraston 2005, MNRAS, 362, 799). The NIR observations of normal galaxies of different morphological types from elliptical to spirals is also showed to be reproduced by stellar population models (Mannucci et al. 2001, MNRAS, 326, 745).
Mid-IR observations are also very important to construct a wider spectral energy distribution (SED) of high-redshift galaxies as the rest-frame near-IR is the key to determine the mass of the galaxy and the unobscured star formation, and to study the older stellar populations.


Bielby et al. 2012
Curtis-Lake et al. 2012
Madau et al. 1996
Mannucci et al. 2001, MNRAS, 326, 745
Maraston 2005, MNRAS, 362, 799
Steidel et al. 1999
Steidel, Pettini & Hamilton 1995
Worthey 1994, ApJS, 95, 107

What can be done with DAG
  • Northern Hemisphere equivalents of VISTA surveys like UltraVISTA, VIDEO, VHS. However repetition of UKIDSS surveys must be avoided.
  • DAG can do surveys to find the Lyman-Break Galaxies in the near infrared. Detailed observations of the known ones can also be done to study the galaxy properties like mass, star-formation and metallicity.
  • Follow-up observations of Gamma-ray Bursts (GRBs) to locate and study the host galaxies of the high-redshift GRBs:
    This requires either a multi-band imager like GROND, at least covering r,z,J,H,K bands, or a spectrograph with a large wavelength coverage like XSHOOTER. An Integral Field Unit (IFU) spectrograph with a FoV of at least 5"x5" to cover the Swift XRT error circle would overcome the problem of locating the GRB for a spectroscopic observation.
  • A complementary project to SAURON to study the galaxy properties in the near-IR without the effects of dust obscuration. The stellar population studies have already started to extend in the near-IR and there are some promising spectral features that can be used to study the galaxy properties (see the above text).
  • Mid-IR observations are also very important to construct a wider spectral energy distribution (SED) of high-redshift galaxies as the rest-frame near-IR is the key to determine the mass of the galaxy and the unobscured star formation, and to study the older stellar populations.


Updates: 11.05.2012 (Aliş)

3.2 Observational Cosmology

Observational studies in cosmology mainly aim one thing: What is the implied density parameter (Ωm) of the universe?

This can be obtained from cosmic background radiation, type Ia supernovae and galaxy clusters. In the standard structure formation scenario (i.e. CDM) clusters are formed at the nodes of the cosmic web (see Millennium Simulation, Springel et al., 2005). Their formation process is still ongoing, is mainly driven by gravitational processes making the abundance of clusters as function of mass and redshift a sensitive probe of mass density parameter and amplitude of mass fluctuations (σ8). Comparison of values obtained from different methods can give new insights and are important for consistency checks. In the near future EUCLID satellite will investigate galaxy clusters to be able to constrain those parameters.

Fig.3.2-1. From the EUCLID Red Book

The Dark Energy implied by a group of astronomers in 1998 by studying type Ia supernovae led to a consiredable interest in using galaxy clusters. It has been implied that the universe is expanding with an accelerating speed. There are new surveys and efforts are being done to characterize better this acceleration. Observations for the Dark Energy Survey (DES) has just started. The Blanco telescope in CTIO (Chile) is used to observe around 1000 type Ia SNe. Dark Energy became the hottest topic in observational cosmology studies. On the other side, Dark Matter is known since 1930s and became almost a standard approach to explain structure formation in the universe. It is still needs to be explained. The nature of dark matter remains unknown but particle physicists and astrophysicists are gathered their power to solve this puzzle. Examples like the Bullet Cluster give very important clues to understand its properties. Therefore investigating merging clusters is another hot topic in observational cosmology. 4m class telescopes are very good opportunuties to focus on individual clusters detected from large surveys.

It has been a while that the third method to obtain cosmological parameters (i.e. CMB) is used extensively. Firstly, COBE (in 1999) and then WMAP (2003) satellites changed our knowledge significantly. Now it is known that the fluctuations in the CMB around orders of 10-5 result structure formation in the universe just after the Radiation Era.

Galaxy clusters amongs these methods always attracts people more than others. Key issues in the determination of cosmological parameters are control and decrease the systematic uncertainties due to our imperfect knowledge of the physics that govern cluster formation and evolution, handle properly the selection function of cluster catalogues. Efforts were made building up large samples of clusters especially since 2000 with the SDSS and before the 2dF survey. These samples were in the low redshift universe (z=0.3-0.4) that is known as local universe in cosmology. To be able to investigate evolution of universe and evolution of clusters itself it is needed to go deeper in terms of redshift. Recently completed CFHTLS, ongoing DES and future LSST are the main surveys to study evolutionary aspects.

As the case is reach large redshifts infrared observations play an important role. Current surveys are designed in multibands but it is not possible to reach beyond z=1.3 with filter set in use (i.e. ugriz). There are efforts to complete current surveys in the IR domain such WIRCAM Deep Survey for the CFHTLS. The DAG project, very likely, may play an important role in this aspect especially when EUCLID considered.


Springel et al., 2005, Nature, 435, 629.

What can be done with DAG
  • Masses of galaxy clusters can be detected via velocity dispersions and these masses can be used to constrain growth rate of structures in the universe. In this sense, spectroscopic follow-ups of clusters which will be detected by DES project and EUCLID satellite can be done with the DAG telescope.


Updates: 11.05.2012 (Aliş)

3.3 Galaxy Clusters

As the most massive bounded objects in the universe, galaxy clusters have a special interest in observatinal cosmology studies. The main research projects can be gathered in three different groups:

  • Constraining the cosmological parameters and dark energy
  • Structural properties, scaling laws and structure formation
  • Internal physics and connection to stellar activity

The state of the art cosmological simulations, like The Millennium Simulation (produced mainly by MPA and ICC (Springel et al. 2005)), show that clusters result from the hierarchical structure formation. Besides enabling the undertanding of internal physics of clusters, numerical simulations play an important role in the determination of selection function of any cluster sample. It became a standard approach today producing numerical simulations before the observations. Comparisons between the simulations and observations give clues about the fine-tuning in the physics as well as technical capabilities and systematics.

Beyond their cosmological interest, galaxy clusters often considered as laboratories because they are closed boxes where all their gaseous matter retained due to high potential well. Main components of clusters are galaxies and the intracluster medium (ICM). In the standard CDM scenario these baryonic components consist the 20% of the total mass in clusters. The remaining part is attributed to the so-called Dark Matter. First claims about such matter was belong to Zwicky (1933) where he noticed the difference between the light and the implied mass in clusters. The very famous Bullet Cluster (1E 0657-558) is a perfect example to investigate different components in clusters, especially Dark Matter. Properties of galaxies within clusters help to understand better the galaxy formation and evolution. With increasing redshift blue galaxies appear more in clusters (Butcher-Oemler effect). Detailed studies of individual clusters are then important to understand evolution of galaxies in clusters. There are many mechanisms (e.g. ram pressure stripping, tidal mergers, harassment) proposed for galaxy interaction in clusters lead to an evolution. This is known as the morphology-density relation of galaxies implies denser environments show more interaction between the member galaxies in clusters (Dressler, 1980).

Interaction related to galaxy clusters not only seen between the member galaxies it is also seen between clusters as merging events. Cluster merging provides information on many physical processes seen in clusters. These events can be studied in the optical, radio and X-rays (Ferrari et al., 2006; Ferrari et al., 2003; Maurogordato et al., 2008; Bourdin et al., 2011). Cluster merging and internal interactions within the clusters are important for star formation studies (Poggianti et al., 2004; Ferrari et al., 2005; Ferrari et al., 2005).

The central galaxies in clusters (aka Brightest Cluster Galaxies - BCG) are also very important to understand and constrain galaxy formation. Hiearchical structure formation fails or not well explains BCGs. Formation of these galaxies mainly happen in the form of galaxy infalls and tidal mergers where they gain gas in some cases. Therefore investigating star formation histories in clusters can be possible with studying BCGs (Quillen et al. 2008; O'Dea et al. 2008; Hicks et al. 2010; Edge et al. 2010). Thanks to the large surveys BCGs spread over a wide range of redshift are known and can be studied.

The first approaches to study galaxy clusters were started with inspecting the Schmidt plates obtained at Palomar Observatory. These efforts was based on visual inspection where today with wide field CCD imagers multi-band observations and cluster detections are done automatically. ESO Imaging Survey (EIS), Sloan Digital Sky Survey (SDSS), 2dF (Two Degree Field Survey), Canada-France-Hawaii Telescope Legacy Survey (CFHTLS) are the most important digital surveys designed for galaxy cluster studies or enabled those studies in the modern era.

These various aspects described briefly above show the need for large, multi-band, homogeneous samples to study clusters as large scale structures of the universe. Starting from SDSS it became possible and will become easier with the recent and future planned surveys. Studying evolution of galaxy clusters needs to go deep where it is needed to extent recent optical multi-band surveys into the IR. The current deepest survey for galaxy clusters, CFHTLS, has just started new programs to add IR data to the survey fields. For this purpse WIRCAM observations started and planned at CFHT under two different programs: CFHQSIR and WIRCAM Deep Survey. The DAG Project becomes even more important in this aspect. VLT VIRMOS is also available at the moment to study extensively clusters depending on time allocation. There are ~69.000 galaxy clusters detected from the SDSS DR6 (Szabo et al. 2011) in 9600 square degrees which makes 7 cluster per On the contrary in CFHTLS ~3500 clusters detected in 174 sq.deg. (Olsen et al., 2007; Olsen et al., 2007; Benoist 2012) which makes 20 cluster per sq. degree. The difference comes from the depth of the CFHTLS which reaches z=1.2-1.3. Certainly, the next generation surveys (e.g. LSST) will change this view significantly.


Benoist et al., in prep
Bourdin et al., 2011, A&A, 527, 21.
Dressler, 1980, ApJ, 236, 351.
Edge et al. 2010, A&A, 518, 47.
Ferrari et al., 2003, A&A, 399, 813.
Ferrari et al., 2005, A&A, 430, 19.
Ferrari et al., 2006, A&A, 446, 417.
Grove, Benoist & Martel, 2009, A&A, 494, 845.
Hicks et al., 2010, ApJ, 719, 1844.
Maurogordato et al., 2008, A&A, 481, 593.
O'Dea et al., 2008, ApJ, 681, 1035.
Olsen et al., 2007, A&A, 461, 81.
Poggianti et al., 2004, ApJ, 601, 197.
Quillen et al., 2008, ApJS, 176, 39.
Springel et al. 2005, Nature, 435, 629.
Szabo et al., 2011, ApJ, 736, 21.
Tran et al., 2005, ApJ, 627, 25.
Zwicky, 1933, AcHPh, 6, 110.

What can be done with DAG
  • Brightest cluster galaxies can be observed in IR to determine star formation rates.
  • Metallicity of the ICM can give clues about the evolution of clusters.
  • MOS spectroscopy of the member galaxies lead to the mass determination and obtain the dynamical status of clusters.
  • With the assumption of a FOV of 30 arcmin it is possible to capture clusters in the redshift range of z>0.05. Which means that with the telescope implied here we cannot do imaging (single shot) of nearby clusters such as Virgo, Fornax, Centaurus, Hydra.


Synergies with Current and Future Facilities

Updates: 04.05.2012 (Tolga)

4.1 High Energy Missions

The future of X-ray astronomy does not look very bright for almost a decade, as there is no new observatory class X-ray satellite in the foreseeable future. However, this does not mean there won't be any X-ray/gamma-ray missions, in fact there will be many of them but in smaller scales. These smaller scale missions will, of course, actually need more cooperation and follow-up observations. Furthermore most of them (including some of the currently operating ones) will always have open data access.

A list and brief descriptions of X-ray/gamma-ray missions, which the author thinks will create follow-up observation opportunities for a ground based optical/NIR 4m class telescope are given below. The list is based on planned or scheduled approximate launch dates:


Swift has been operating since November 2004. Swift has a complement of three co-aligned instruments: the Burst Alert Telescope (BAT), the Xray Telescope (XRT), and the Ultraviolet/Optical Telescope (UVOT). The whole purpose of the largest instrument, BAT, on SWIFT is to monitor almost a sixth of the entire sky to detect transient events, often GRBs it is sensitive to 15-150 keV. After the detection SWIFT will autonomously repoint itself to aim the XRT and UVOT at the transient event to obtain high-precision X-ray and optical positions and X-ray spectra to be determined. This satellite has been acting as an all sky monitor since its launch and creating many opportunities for ground based telescopes. All of the data this satellite obtains is open and it almost always needs further follow-up observations by ground based telescopes (see notes on GRBs or notes on the near-infrared observations of Galactic black hole candidates). Finally, it is seen as one of the most successful missions by NASA (by means of its effectiveness) therefore it will be operating for quite a long time, depending on the health of the satellite. It is also the only "all-sky" monitor at these energies at the moment.


Fermi is a gamma-ray mission launched in 2008. It has two main detectors. LAT (Large Area Telescope) is a gamma-ray detector with a wide field of view (one-fifth of the whole sky) and is approximately sensitive to the energy range 30 MeV - 300 GeV. Again all of the data this satellite obtains is public immediately and this satellite has also been creating many opportunities for ground based telescopes some examples are of course monitoring of active galaxies, follow-up observations of GRBs etc.

nuSTAR (The Nuclear Spectroscopic Telescope Array Mission)

nuSTAR will be the first imaging telescope at hard X-rays. Its launch date is planned as this summer. The telescope will be sensitive to 5-80 keV range and will have a focal length of 10 m yielding images with FWHM 10 arc seconds. The field of view will be about 13x13 arc minutes so this will not be an "all-sky" monitor. However with its imaging capability and long exposures it will be able observe a number of obscured AGN, which are hard to detect in the soft X-rays. Again all of the data this satellite will obtain will be public immediately.

SRG (Spectrum-Roentgen-Gamma)

SRG is a German-Russian mission with an ambitious gaol of surveying the whole sky in the soft (with eROSITA) and hard (ART-XC) X-rays for about 4 years. The aim is to detect the hot intergalactic medium of 50-100 thousand galaxy clusters, to detect systematically all obscured accreting Black Holes in nearby galaxies and many (up to 3 Million) new, distant active galactic nuclei and to study the Galactic X-ray source populations. The word detect is important because often this is what this satellite will only be able to do. So it will create many great opportunities for ground based telescopes. In fact they are planning to use RTT150 as one of their main telescopes to obtain low resolution optical spectra of some of the objects SRG detects. However the data policy is not very clear and we may need to wait several years to reach their catalog of sources.

LOFT (Large Observatory for X-ray timing)

LOFT is a proposed mission to ESA with a planned launch date somewhere in 2020s. The plan is to have a detector that has about 12m2 photon collecting area @ 8 keV, which is about a factor of 20 larger than RXTE PCA. Basically it is being planned as the almost ultimate X-ray timing mission for observations of Galactic neutron stars, black-holes, X-ray binaries and some extragalactic sources. Clearly it will detect a number of new sources and will create many opportunities for ground based observations.


What can be done with DAG and
What DAG needs to have in order to be successful

All of the Galactic or extra-galactic high energy sources also emit in optical and near-infrared wavelengths and it will only be possible to understand the nature of these sources by performing observations in coordination with X-ray / gamma-ray satellites and cover the wides possible wavelength range. Some example projects have already been given in this document (see the discussion about the gamma-ray bursts or the Galactic black hole transients), more examples can be given. However, in order for a 4m class telescope to be successful in these observations it should have a number important capabilities.

  • Apart from routine monitoring of Active Galactic Nuclei or observations of clusters of galaxies most of the high energy sources in the universe are seen as sudden events which have timescales from a couple hours to weeks or months (eg. Dwarf Noave, Classical Recurrent Novae, X-ray Transients). Therefore a succesful "followup telescope" should have a flexible schedule for Target of Opportunities.
  • Apart from Active Galactic Nuclei (Blazars etc.) most of the high energy sources show very short timescale variations in order to be able capture the whole variability timescales it is essential to obtain a detector that would have high time resolution. A CCD that is very effective and has high quantum efficiency will be very important in that sense as often the minimum exposure times will be determined not by the capabilities of the CCD but by the source detection and signal to noise ratio. See the discussion about black hole transients.
  • IR wavelengths are the best region of electromagnetic spectrum where one can study the secondary stars in CVs and LMXBs. Spectroscopic studies, elemental abundance determination, irradiation, and classification among the species can be effectively done in near-IR regime. The up coming new X-ray and Gamma-ray missions will be detecting over thousands of new X-ray sources. Follow up observations of the IR counterparts to these sources which include new CVs and X-ray binaries will very important. This needs effective ground-based telescopes devoted to followup observations.
  • Finally, it is very important that the mirror coating should be done in way that allows high reflectivity both in the optical and near-IR telescope. This can definetely be a distinctive property of this telescope with the power of covering the widest possible wavelength range simultaneously or near-simultaneously. This means that the observatory will need to buy two detectors (a NIR imager and an optical CCD). And also the mirror coating should be selected more carefully. I suggest checking the following links: Why Silver, Silver vs. Aluminum


Updates: 14.05.2012 (Aliş, Aybüke)

4.2 Optical

TUG (TUBITAK National Observatory)

TUG is the only national observatory of Turkey which currently hosts RTT150 (1.5 m telescope) as the largest telescope. The observatory plans to have a larger one in the near future. DAG project can create synergy with TUG especially in the context of making simultaneous observations in different wavelengths or with different techniques such as imaging can be done at TUG whereas spectroscopy at DAG. The most likely science topics that will benefit from such a synergy are transient phenomenons. In the case of TUG having a larger telescope, exchanging observing runs or conducting complementary observations can be done especially if the weather conditions are considered.

VLT Survey Telescope (VST)

VST is a 2.6-m telescope installed at Paranal, Chile. It is equipped with a 268-megapixel camera called OmegaCAM with a total FoV of 1 degree x1 degree. VST is dedicated to survey programmes that have started in 2011:

  • The Kilo-Degree Survey (KIDS) - PI Konrad Kuijken (Leiden)
    This survey aims to image 1500 square degrees in 4 bands (to be complemented in the near-infrared with data from the VIKING survey). The survey aims to cover this large area to a depth 2.5 magnitudes deeper than the Sloan Digital Sky Survey (SDSS), with considerably better image quality. The primary science driver for the design of this project has been weak gravitational lensing. The science goals of the KIDS project are numerous, including: studying dark matter halos and dark energy with weak lensing, investigating galaxy evolution, searching for galaxy clusters, and looking for high redshift quasars. The KIDS project fills an important niche in lensing surveys between smaller, slightly deeper surveys, such as the CFHT Legacy Survey, and larger, shallower surveys like the SDSS.
  • The VST ATLAS - (PI: Tom Shanks; Durham)
    This survey is targeting 4500 square degrees of the Southern Sky in 5 filters to depths comparable to the SDSS. This survey will also be complemented with near-infrared data from the VHS VISTA survey. The primary science driver is to determine the dark energy equation of state by examining the 'baryon wiggles' in the matter power spectrum, via surveys of luminous red galaxies using both photometric and spectroscopic redshifts. But this survey will also provide the imaging base for many other future spectroscopic surveys, both at the VLT and also via wide-field fibre spectrographs such as the new AAOmega instrument at the Anglo-Australian Observatory. For example, the VST ATLAS will be valuable in the hunt for high redshift galaxies and quasars.
  • VPHAS+ - The VST Photometric H-α Survey of the Southern Galactic Plane (PI: Janet Drew (Imperial))
    This survey will combine H-α and broadband u'g'r'i' imaging over an area of 1800 square degrees capturing the whole of the Southern Galactic Plane within the latitude range |b| < 5 degrees. VPHAS+ will facilitate detailed extinction mapping of the Galactic Plane, and can be used to map the structure of the Galactic disk and its star formation history. The survey will yield a catalogue of around 500 million objects, which will include greatly enhanced samples of rare evolved massive stars, Be stars, Herbig and T Tau stars, post-AGB stars, compact nebulae, white dwarfs and interacting binaries. This survey is complementary to IPHAS, a survey of the Northern Galactic Plane nearing completion, but VPHAS+ will include more filters and will achieve better image quality.

DES (Dark Energy Survey)

Currently ongoing the Dark Energy Survey is done in the southern hemisphere using CTIO's 4m Blanco telescope. It can be a very good opportunity to complete DES in the north. It should not necessarily be complementary but a way to contribute DES project can be implemented. IR plays a very important role in the high redshift regime.

DES will be complemented by VISTA in the southern hemisphere, similarly SDSS can be complemented with DAG in the northern hemisphere (especially for declinations > 60 degrees) especially after UKIRT ceases its operations.

Follow-up to EUCLID - (Red Book)

ESA approved the space mission EUCLID to fly. If everything goes with the schedule it will be launched in 2019. This is the most important thing that DAG project can contribute. EUCLID will observe galaxy clusters to obtain mass density parameter of the universe and that way the geometry of the universe can be constrained. Moreover many interesting individual clusters will be detected with EUCLID to study internal physics of clusters besides cosmological purposes. At the point of making follow-up studies DAG may play an important role in the EUCLID era.

The mission will investigate the distance- redshift relationship (galaxies and clusters of galaxies out to z~2) and the evolution of cosmic structures in 6 years life-time. It will cover 15 000 deg² in a wide extragalactic survey by 1.2 m korsch telescope, plus a deep survey covering an area of 40 deg². Field-of-View is ~0.5 square degrees in VIS (Visual imaging) and ~0.6 in NISP (NIR photometry and spectroscopy). It will be launched around 2019.

Follow-up to CFHTLS

CFHTLS has completed in an area totally 174 sq. degrees. Follow-up studies to complete the survey in the IR domain has just started using WIRCAM attached to the CFHT. But so far only Deep Survey of the CFHTLS has been approved which is 4 sq. degree. If CFHTLS-Wide will stay untouched in the IR, DAG may contribute as well. But this has less priority than the first two items above.

Updates: 11.05.2012 (Aliş)


GAIA is an ambitious mission imaging 1 billion stars, millions of galaxies, quasar, planets and focusing on average 70 times to each object in 5 years by using two different types of telescope systems and a very big CCD.

  • Science: the Milky Way, extrasolar planetary, brown dwarfs, astroids, exploding stars, general relativity
  • Astrometry: accurate measurements, even in densely populated sky regions of up to 3 million stars/deg2
  • Photometry: continuous spectra in the band 320-1000 nm for astrophysics and chromaticity calibration of the astrometry
  • Spectrometry: high resolution, grating, narrow band: 847-874 nm

GAIA will have two "photometers" the blue photometer will be sensitive to 320-660nm whereas the Red Photometer will be sensistive to 650-1000nm.

The survev will cover a magnitude range of 6 < V < 20 mag. with about 109 objects. However only down to the 15th mag the positional accuray will be 10-25 µarcsec. It will be able to measure radial velocity of stars with V < 16-17 mag using the spectrometer with a resolution of 15km/s.

GAIA should be one of the ultimate targets for a 4m telescope to perform followup observations.

  • It will be a unique mission however it will need near-IR coverage at areas where the optical extinction will be significant. If you think of it it will be able to detect an object at 15th mag with zero extinction. However if the source is in a location where there is 5 mag optical extinction that it will only be barely detected, whereas in K band the extinction will be only 0.5 mag.
  • It will need radial velocity measurements for faint stars.
  • It will be detecting a number of RR Lyrae variables etc. but the cadence of those observations will be very low hence further follow-up observations will be necessary to to be able to observe these stars (determine the periods etc.). These observations will allow for an independent determination the reddening and their distances (see e.g. Kunder et al. 2010), which will complement the parallax measurements.
  • It will also detect a number of transient events a 4m class telescope may be able to perform real good follow-up observations of these events as the GAIA will not be a pointing satellite.
  • Finally note that all of the advertised properties of GAIA are the values at the end of the mission, which is planned to be 2020. Before that everything will be much lower. For example spectrum of an F3 giant V=16 mag no extinction will have a S/N of 7 in a single measurement only when you add all of the spectra you obtain for the same star during the whole mission you will have a S/N of 130.


Kunder et al. 2010

What can be done with DAG
  • Some time can be allocated to detect type Ia supernovae.
  • Observing individual clusters using MOS type spectrographs leads reliable mass determinations and gives dynamical status of the clusters.
  • Follow-up CFHTLS in the NIR domain to complete the dataset obtained in the optical already.


Updates: 11.05.2012 (Aybüke)

4.3 Near-IR

Visible and Infrared Survey Telescope for Astronomy - VISTA

VISTA is a 4-m class wide field survey telescope for the southern hemisphere located at ESO's Cerro Paranal Observatory in Chile, equipped with a near infrared camera (1.65 degree diameter field of view at VISTA's nominal pixel size) containing 67 Megapixels camera and 5 broad band filters at Z, Y, J, H, Ks and a narrow band filter at 1.18 micron.

VHS - VISTA Hemisphere Survey - (PI Richard McMahon; Cambridge)

The VHS will image the entire ~20 000 square degrees of the Southern Sky, with the exception of the areas already covered by the VIKING and VVV surveys, in J and Ks. The resulting data will be about 4 magnitudes deeper than 2MASS and DENIS. The 5000 square degrees covered by the Dark Energy Survey (DES), another imaging survey scheduled to begin in 2010 at the CTIO 4 metre Blanco telescope, will also be observed in H-band. The area around both of the Galactic Caps will be observed in Y- and H- band as well to be combined with the data from the VST ATLAS survey. The main science drivers of the VHS include: examining low mass and nearby stars, studying the merger history of the Galaxy, measuring the properties of Dark Energy through the examination of large-scale structure to a redshift of ~1, and searches for high redshift quasars.

VISTA Deep Extragalactic Observations Survey - VIDEO - (PI Matt Jarvis; Hertfordshire)

VIDEO is a 12 square degree Z, Y, J, H, Ks survey to study galaxy evolution as a function of epoch and environment to redshift of ~4 using active galactic nuclei, galaxy cluster evolution, and very massive galaxies. The survey comprises three fields: the Chandra Deep Field South, 4.5 square degrees of the XMM-Newton Large-Scale Structure Survey, a field of the European Large-Area ISO Survey. The width and area of VIDEO are intermediate between the wide but relatively shallow VIKING survey and the small, but very deep, Ultra-VISTA.

VISTA Kilo-Degree Infrared Galaxy Survey (VIKING; PI: Will Sutherland (Cambridge))

The VIKING survey provides an important complement to the optical KIDS project. VIKING will image the same 1500 square degrees of the sky in Z, Y, J, H, and Ks to a limiting magnitude 1.4 mag deeper than the UKIDSS Large Area Survey. The near-infrared data will be used in the determination of very accurate photometric redshifts, especially at z > 1, an important step in the weak lensing analysis and the observation of baryon acoustic oscillations. Other science drivers include the hunt for high redshift quasars, galaxy clusters, and the study of galaxy stellar masses.

The survey region may be modified slightly as the survey progresses but the nominal RA and Dec limits are shown below:

 SGP:     22h00 < RA < 03h30,  -36 < Dec < -26 deg. 
 NGP:     10h00 < RA < 15h30,   -5 < Dec < +4 deg 
 GAMA09:  08h36 < RA < 09h24,   -2 < Dec < +3 deg. 

UltraVISTA - (Jim Dunlop, Edinburgh; Marijn Franx, Leiden; Johan Fynbo (Copenhagen), Olivier LeFèvre, Marseilles)

Ultra-VISTA aims to image one patch of the sky (the COSMOS field) over and over again to unprecedented depths. The survey will use the Y, J, H, and Ks broadband filters along with one narrow-band filter specifically designed to study Lyman-a emitters at redshift 8.8, of which ~30 are expected to be found with this survey. The science goals of Ultra-VISTA include studying the first galaxies, the stellar mass build-up during the peak epoch of star formation activity, and dust obscured star formation.

NOAO Extremely Wide-Field Infrared Imager - NEWFIRM

28x28 arcmin FoV imager; covering 1-2.4 microns at 0.4"/pixel; mounted on 4-m NOAO telescope.

This detector is decommissioned at the moment. It may however be a good starting detector for DAG if an agreement with the NOAO could be made.

Updates: 10.05.2012 (Korhan)

4meter-Multi Object Spectroscopic Telescope - 4MOST

  • 4meter-Multi Object Spectroscopic Telescope Survey will be used with VISTA or NTT
  • for follow-up observations of GAIA, eROSITA, EUCLID
  • ESO final decision in 2013
  • PPT

Updates: 11.05.2012 (Aliş)

ESO New Technology Telescope - NTT

The ESO New Technology Telescope (NTT) is an Alt-Az, 3.58m Richey-Chretien telescope which pioneered the use of active optics. The telescope and its enclosure had a revolutionary design for optimal image quality.

The ESO New Technology Telescope, NTT, was commissioned in 1989, and completely upgraded in 1997 (Big Bang). It has an alt-az mounting, and two Nasmyth focii, which host two instruments. SUSI2 is mounted on Nasmyth A, while since 21 June 2008 EFOSC2 is mounted on Nasmyth B. The pointing error is about 1.5" RMS, but degradation occurs close to zenith and at zenith angle larger than 60 degrees. The pointing is limited to 70deg. zenithal distance, and 3 degrees from zenith.

NTT uses Sofi as the spectro-imager in the NIR regime (1-2.5 microns)

James-Webb Space Telescope - JWST

NASA, ESA, CSA space mission. To be launched in 2018.


ESA space mission to be launched in 2019

Near – Infrared Sky Surveyor (NIRSS)

The Near-Infrared Sky Surveyor (NIRSS) is a new mission concept, still in the early days of formulation (pre-phaseA), based on the requirements of ASTRO2010 decadal survey report, New Worlds, New Horizons in Astronomy and Astrophysics (NWNH). An assessment report was prepared for whether it will be a counterpart project to the EUCLID or not.

NIRSS will deeply map the entire sky at near-infrared wavelengths by using a 1.5-meter telescope to reach full-sky 0.2 µjy (25.6 mag AB) sensitivities in four pass-bands from 1 to 4 µm (J, H, K, L bands) in a 4-yr mission. NIRSS will be ~3000 times more sensitive than 2MASS, ~500 times more sensitive WISE, 10 times deeper than VISTA-VIDEO and 5 times deeper than VLT with slightly better spatial resolution and across the full sky. It will be also well matched to the next generation of deep (~0.1 µJy), wide area (>2π ster), ground-based optical surveys (LSST and PAN-STARSS). While ultra-deep infrared images have only recently been obtained over small areas, NIRSS will build on these achievements by providing ultra-deep near-infrared images across the entire sky.

The Astro2010 Decadal Survey gave its highest recommendation in the large-scale space mission category to WFIRST, a Wide-Field Infrared Survey Telescope with both imaging and spectroscopy capabilities. WFIRST includes science objectives in exoplanet exploration, dark energy research and galactic and extragalactic surveys by using a combination of three proposed telescopes: the Microlensing Planet Finder (MPF), the Joint Dark Energy Mission/Omega (JDEM-Omega) and the Near-Infrared Sky Surveyor (NIRSS).

Fig-4.3-1. Left panel: Depth at 2.2μm vs. area for NIRSS and various ground-based surveys. Right panel: Sensitivity vs. wavelength. NIRSS will complement the next generation of deep ground-based surveys (ASTRO2010_NIRSS – Daniel Stern).

As shown in Fig.1, when NIRSS is launched, it will be quite powerful survey rather than other ground base like VISTA, UKIDSS, etc. or space projects like 2MASS, WISE, etc.

Table-4.3-1. Predicted numbers of high-redshifts.

Especially for the high redshift objects, due to NIRSS cover all sky deeply, it will detect large number of objects back in time when compared with 4m class telescope surveys. DAG project is also planned as the same class telescope like UKIDSS or VISTA. Furthermore, other current and planned space-based infrared missions either have too small of a FOV (e.g., JWST), work too far into the infrared (e.g. SPITZER and WISE) or do not work sufficiently far into the near-infrared background from primordial stars.

Fig-4.3-2. The point source sensitivity of various planned weak gravitational lensing surveys: LSST (red), WFIRST deep (blue) and Euclid wide (green). Magnitudes are defined so that fainter objects have larger magnitudes. LSST, Euclid’s broad band optical images, and WFIRST deep survey will be able to see fainter galaxies than Euclid’s wide survey. The WFIRST deep survey goes deeper, but the Euclid survey covers a much larger area. SOURCE: Courtesy of Chris Hirata, California Institute of Technology.

LSST will improve photometric redshifts for well-detected galaxies at z>1 whereas NIRSS will study very clearly around z~4.

Scaling from the VISTA and UKIDSS programs, which will be shallower than NIRSS over <0.1% of the sky using dedicated multi-year surveys on 4-meter class telescopes, full-sky near-infrared images at the 0.2μJy depth would require a network of hundreds of 4-m class telescopes operating for nearly a decade. Although NIRSS can push the limits, it's still a concept mission besides EUCLID.


J, H, K', K, Ks, HeI, Pa gamma, Pa beta, (:cell PQA(PSS(FeII):), CO band, K cont.



What can be done with DAG

DAG can help extending the existing VISTA survey fields with observations at the northern hemisphere. However without an extremely large field of view, it is obvious that DAG can not do "time resolved survey observations" of the whole or a large part of the survey. However, a NIR survey of the SDSS fields above +60 degrees declination may be very useful.

For the other satellites mentioned above best would be to obtain follow-up observations including imaging and and spectroscopic observations. Furthermore optical observing capability may turn out to be very useful for the follow-up observations of some of the infrared satellites.


Updates: 14.05.2012 (Korhan)

4.4 Mid/Far-IR

The Mid-Infrared Instrument (MIRI)

The Mid-Infrared Instrument (MIRI) on JWST will provide direct imaging and medium resolution spectroscopy (R~3000) over the wavelength range 5-28.3 micron. Coronagraphic imaging at 10.65, 11.4, 15.5 and 23 micron, and low resolution spectroscopy (R~100) over the wavelength range 5-10 micron. "MIRI" is expected to make significant contributions to all four of the primary science themes for JWST:

  1. Discovery of the "first light".
  2. Assembly of galaxies: history of star formation, growth of black holes, production of heavy elements.
  3. How stars and planetary systems form,
  4. Evolution of planetary systems and conditions for life.

MIRI will use the Lyman break technique to identify objects at increasing redshifts up to z = 30 or higher. More detailed follow-ups are being planned for the brightest first light source candidates by MIRI.

MIRI will use near-infrared spectroscopy at R = 100 will be needed to verify the photometric redshifts and will observe spectroscopic follow up at R = 1000 aimed at measuring the Balmer line intensities will provide star formation rates and estimates of the dust content. It's being planned to obtain high signal-to-noise, R = 1000, near-infrared spectra of QSOs or bright galaxies identified in other surveys.

Wide-Field Infrared Survey Explorer - WISE

MID-IR survey Science

  • Asteroids
  • Brown Dwarfs
  • AGNs
  • Ultra-Luminous Galaxies


MIRI Science-Requirements

What can be done with DAG
  • The DAG can study detect bright far objects or QSOs in a dedicated deep or ultra-deep survey and this can be provide a basis for MIRI.
  • The DAG telescope can make spectroscopic follow-up observations in greater resolutions, if DAG has a high-resolution spectroscopic instrument in near-infrared.


Updates: 09.05.2012 (Umut)

4.5 Sub-mm/Radio

Follow-up to Star Formation Studies

In star-formation, the protostellar envelope is surrounded by large amounts of cold gas and dust particles which reduces the intensity of the light reflecting from the protostar. Therefore the detection of low-mass protostars in their early phases is hard at optical and infrared wavelength regimes. However, it is very common to observe such cold objects at the longer wavelengths such as submillimeter and millimeter wavelengths. With the evolution of the protostellar phase from molecular cloud to protoplanetary disks, the observation wavelengths are also evolves from mm to IR. A 4m+ class ground based IR telescope can be very useful to follow-up the observations of current and old IR/submm space missions, together with the large surveys.

Follow-up to ALMA

ALMA (de Graauw et al) is a new state-of-art submm/mm observation facility recently commisioned. The observatory has 66 antennas with a 12 metre size antennas. Many of the sources observed with ALMA can also be followed-up with DAG.

Follow-up to Herschel

Herschel Space Observatory (Pilbratt et al. 2010) is a cornerstome mission of ESA, a far-IR/submm telescope with a 3.5~metre diameter. It was launched in May 2009 and orbiting at the L2 position of Earth with an estimated lifetime of around 3.5 years.

Follow-up to other Single-Dish Facilities

Other mm/submm telescopes include, James Clerk Maxwell Telescope (JCMT, 15m), IRAS 30m, Atacama Pathfinder Experiment (APEX, 12m), Nobeyama Radiotelescope (40m), Onsala Raditelescope (20m), Caltech Submillimeter Observatory (CSO),

Follow-up to other Interferometer Facilities

Other mm/submm interferometers include, Submillimeter Array (SMA), extended Submillimeter Array (eSMA), Plateu de Bureau Interferometer (PdBI)


What can be done with DAG


Competition in the Northern Sky

Updates: 12.05.2012 (Tolga, Aybüke)

5.1 Current and Future Projects with 4m-class Telescopes

United Kingdom Infra-Red Telescope - UKIRT

UKIRT is a 3.8-m telescope located at Mauna Kea, Hawaii. It is equipped with the Wide-Field Camera (WFCAM). WFCAM is a near-infrared camera which consists of 4 Rockwell Hawaii-II (HgCdTe 2048x2048) arrays spaced by 94% in the focal plane, such that 4 separately pointed observations can be tiled together to cover a filled square of sky covering 0.75 square degrees with 0.4 arcsecond pixels. WFCAM contains 8 filter paddles, one of which holds blanks for taking dark frames and blanking off the arrays, whilst each of the 7 remaining paddles contains a set of 4 science filters and a clear autoguider filter. The science filters of WFCAM are Z, Y, J, H, K and two narrow-band filters.
The current main project conducted via UKIRT is the UKIRT Infrared Deep Sky Survey (UKIDSS) and the future main project is the UKIRT Hemisphere Survey (UHS). The details of these surveys can be found in the "Current and Future Survey Projects" section.

At the moment it looks like this telescope is going to be decommissioned by 2013.

NASA Infrared Telescope Facility - IRTF

3m telescope with NIR spectroscopic instruments

Updates: 11.05.2012 (Aliş)

William Herschel Telescope - WHT

WHT is a 4.2 meter telescope and main available instruments at WHT are:

  • ISIS - single-slit spectroscopy, R < 10000, 4' slit, spectro-polarimetry
  • LIRIS - IR spectroscopy, R < 4000, and imaging, 4' field
  • ACAM - optical imaging, low-resolution spectroscopy, 8' field
  • Prime-focus imager - optical imaging, 16' field
  • AF2/WYFFOS - multi-object fibre-fed spectroscopy, R < 9000, 40' field
  • NAOMI/OASIS - integral-field spectroscopy with or without natural-guide-star adaptive optics (NGS AO), R < 4000, 17" field
  • NAOMI/INGRID - IR imaging with or without NGS AO, 40" field (coronagraphy is also possible, with OSCA, 25" field)

Updates: 11.05.2012 (Aliş)

Telescopio Nazionale Galileo - TNG

TNG is 3.58m Alt-Az telescope equipped with an active optics system. Its 2 Nasmyth foci host 5 instruments which are permanently mounted and operating at La Palma (Canary Islands).

Updates: 11.05.2012 (Aliş)

Wisconsin Indiana Yale NOAO Telescope - WIYN

WIYN is a 3.5 meter telescope located at Kitt Peak (NOAO). WHIRC is the main NIR imager up to 2.5 microns.


What can be done with DAG
  • UKIRT Hemisphere Survey will be a one time imaging survey therefore spectroscopic follow-ups of the newly detected sources and also observations of interesting sources in longer timescale can be done with DAG.


Updates: 10.05.2012 (Tolga)

5.2 Current and Future Survey Projects

Updates: 11.05.2012 (Aliş)

CFHQSIR (CFHTLS Y-band WIRCam Large Program)

The CFHQSIR* survey consists in WIRCam Y-band imaging of the 171 CFHTLS Wide fields distributed over four patches across the sky. The main scientific objective of CFHQSIR is to search for quasars at redshifts ~7 (the principal investigators are J.-G. Cuby for France & C. Willott for Canada). CFHQSIR will also detect brown dwarfs and complement the CFBDSIR program. As a near IR counterpart of the CFHTLS, CFHQSIR will be of general interest to a large community of CFHTLS users.

Each WIRCam pointing (20'x20' field of view, 9 WIRCam pointings are needed to cover one single one square degree MegaCam tile) consists of 4-dithered 75 second Y-band exposures split in two 2-exposure visits separated by at least 20 days. At the end of the survey, all four CFHTLS Wide patches made from a total of 171 MegaCam pointings will lead to a sky coverage of 150 sq.deg. once the overlaps between pointings and gaps have all been accounted for. The depth of the total 5mn integration will be defined by the ~0.6" median image quality and low to medium sky background.

Updates: 11.05.2012 (Aliş)

WIRCAM Deep Survey (WIRDS)

WIRDS is a program devoted to detect galaxy clusters using CFHTLS optical data added with NIR observations are being taken with WIRCAM attached to the CFHT. So far program focused on the Deep fields of the CFHTLS due to limited time allocation. Inclusion of NIR data to the optical CFHTLS data it will become possible to detect galaxy clusters further than z>1.1.

Updates: 12.05.2012 (Aybüke)

UKIRT Infrared Deep Sky Survey - UKIDSS

UKIDSS is the next generation near-infrared sky survey, the successor to 2MASS. UKIDSS began in May 2005 and surveyed 7500 square degrees of the Northern sky, extending over both high and low Galactic latitudes, in JHK to K=18.3. This depth is three magnitudes deeper than 2MASS.

UKIDSS consists of 5 different surveys: Large Area Survey (LAS), 4000 sq. degs, K=18.4; Galactic Plane Survey (GPS), 1800 sq. degs, K=19.0; Galactic Clusters Survey (GCS), 1400 sq. degs, K=18.7; Deep Extragalactic Survey (DXS), 35 sq. degs, K=21.0; Ultra Deep Survey (UDS), 0.77 sq. degs, K=23.0.

Four of the principal quarry of UKIDSS are: the coolest and nearest brown dwarfs, high-redshift dusty starburst galaxies, elliptical galaxies and galaxy clusters at redshifts 1‹z‹2, and the highest-redshift quasars, at z=7.

UKIRT Hemisphere Survey - UHS

The aim of UHS is to survey Dec < 60 deg in K <~18.2 and J (and H later on) especially the areas that were not covered by UKIDSS and thus to be the Northern sky equivalent of the VISTA VHS survey.

Updates: 14.05.2012 (Korhan)

The Synoptic All-Sky Infrared Survey - SASIR

SASIR is a dedicated wide-field (1degree diameter) large aperture telescope (6.5m in diameter) project aiming deep and synoptic imaging of the whole Northern sky simultaneously in NIR bands (Y, J, H and K) with four independent focal planes.

Fig-5.2-1. SASIR-UKIDSS-VISTA numbers in z.

It is submitted to the "Optical and IR astronomy from the ground" program prioritization panel of the Astro2010 Decadel Survey.

In the mountains of Baja California, at the San Pedro Mártir (SPM) Observatory, a 6.5 meter telescope will be constructed over the next several years. The JHKs survey, based upon a camera with ~124 2k x 2k IR arrays and a field of view of 0.7 degrees, is expected to begin in 2017 and last for 4 years. The aim is to repeatedly image the sky to a level 100 - 500 times deeper than the 2MASS survey, uncovering the most distant objects and revealing the transient universe. whitepages

Updates: 14.05.2012 (Korhan)

The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST)

The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) is a National Major Scientific Project undertaken by the Chinese Academy of Science. The site is about 100 miles northeast of Beijing, China. The large, 4-meter mirror of LAMOST enables it to obtain spectra of faint objects. LAMOST is designed with 4000 optical fibers in the optical path, covering a large region of the sky simultaneously. This unique system will be used to conduct a survey of 10 million stars in our Galaxy, as well as millions of distant galaxies, over a 5-year period. LAMOST can thus obtain spectra of more than 10000 stars per night, and more than 2 million stars per year.

The LAMOST Experiment for Galactic Understanding and Exploration (LEGUE) is a survey that will obtain spectra of roughly 8 million stars selected for the detailed study of our Milky Way Galaxy.

Resolution(s): R=1800, 5000, Wavelength range: 3700-9000 Angstroms (R=1800 mode) and field of view is 5 degree.

LAMOST will survey at least 2.5 million Galactic halo stars selected from SDSS imaging (where available - otherwise, targets will be chosen from the XuYi survey, PanSTARRS, or SuperCOSMOS photometry) with |b| > 20°. The spheroid survey will cover at least 5000 square degrees in two contiguous sky areas in the north and south Galactic caps, at a density of at least 320 stars per square degree.Fibers will be assigned to targets based on a simple, uniform set of selection criteria using g, (g-r), (u-g), proper motion, and weighted random sampling to ensure a statistical sample is obtained that can be used to infer the characteristics of the stellar populations probed. It started to observe in October 24, 2011 and will continue over 5 years.



What can be done with DAG
  • Perform complementing observations especially in the near-IR.
  • The LAMOST Experiment for Galactic Understanding and Exploration (LEGUE) survey is an on-going project and it will have low resolution data (spectroscopic resolution 1500-5000) in next 5 years. It will provide lots of new objects and by using its MOS-fiber instrument it will have a big amount of object numbers. It's necessary to compete with this size of survey DAG may need a kind of MOS and high resolution instrument at all.
  • DAG and SASIR projects will cover the northern sky and especially in same infrared range(JHK) in approximately the same years. In near future, DAG should have abilities to make deep or ultra-deep surveys or well-design instruments for deep objects.