Coma Cluster Treasury Survey

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Coma Cluster Treasury Survey
Alister W. Graham (Swinburne), Helmut Jerjen
(ANU), Terry J. Bridges (AAO Aust. Gemini
Office) and David Carter (P.I.), Habib
Khosroshahi, Mustapha Mouhcine, Susan Percival
(Liverpool John Moores University, UK) Harry
Ferguson, Paul Goudfrooij (Space Telescope
Science Institute, USA) Thomas Puzia (Dominion
Astrophysical Observatory, Canada) Carlos del
Burgo (Dublin Institute For Advanced Studies,
Ireland) Bryan Miller (Gemini Observatory,
Southern Operations, Chile) Bianca Poggianti
(INAF - Osservatorio Astronomico di Padova,
Italy) Alfonso Aguerri, Marc Balcells (Instituto
de Astrofisica de Canarias, Spain) Derek Hammer
(Johns Hopkins University, USA) Reynier
Peletier, Edwin Valentijn, Gijs Verdoes Kleijn
(Kapteyn Astronomical Institute, Netherlands)
Peter Erwin (Max-Planck-Insitute for
Extraterrestrial Physics, Germany) Ann
Hornschemeier (NASA Goddard Space Flight Center,
USA) Yutaka Komiyama, Masafumi Yagi (National
Astronomical Observatory of Japan, Japan)
Jennifer Lotz (National Optical Astronomy
Observatories, AURA, USA) Neal Miller (National
Radio Astronomy Observatory Johns Hopkins
University, USA) Eric Peng (Peking University,
China) Dan Batcheldor, David Merritt (Rochester
Institute of Technology, USA) Ronald Marzke (San
Francisco State University, USA) Avon Huxor,
Steve Phillipps, James Price (University of
Bristol, UK) Bahram Mobasher (University of
California - Riverside, USA) Neil Trentham
(University of Cambridge, UK) John Lucey, Ray
Sharples, Russell Smith (University of Durham,
UK) Rafael Guzman, Carlos Hoyos (University of
Florida, USA) Kristin Chiboucas, R. Brent Tully
(University of Hawaii, USA) Shardha Jogee
(University of Texas at Austin, USA) Sadanori
Okamura (University of Tokyo, Japan) Jonathan
Davies (University of Wales, College of Cardiff,
UK) Michael Hudson (University of Waterloo,
Canada).
Project website http//astronomy.swin.edu.au/com
a
Overview The heart of the Coma Cluster Treasury
Survey is a Cycle 15 Hubble Space Telescope (HST)
/ Advanced Camera for Surveys (ACS) Treasury
Program (Carter et al. 2008, ApJS, v.176,
p.424-437) that was designed to survey both the
core and an infall region of the richest local
cluster of galaxies the Coma cluster. The
observations contain thousands of galaxies down
to apparent magnitudes g27.5 and I26.6 mag. In
addition, numerous supporting ground-based and
space-based observing campaigns are being
undertaken at other wavelengths. This shall
result in a large, multi-wavelength, public
database of calibrated images and derived
catalogs.
Galaxy Evolution Explorer (GALEX) has delivered
near- and far-UV images of the Coma cluster. The
UV emission from galaxies can originate from
either young stellar populations or old post
main-sequence stars in evolved galaxies. We are
using this data to estimate the stellar ages of
galaxies at various stages of their evolution.
(P.I. Derek Hammer Ann Hornschemeier)
The Spitzer Space Telescopes Infrared Array
Camera (IRAC) has performed a wide-field survey
of the Coma Cluster. The resulting 3.6 ?m galaxy
luminosity function (LF) has revealed an
intriguingly large population of faint red dwarf
galaxies, giving a faint-end LF slope of -2.18 in
the cluster core region. (P.I. Leigh Jenkins)
The X-ray Multi-Mirror Newton telescope is
providing X-ray images. It has a larger
field-of-view and aperture than Chandra, and is
therefore more sensitive although the image
resolution is 5 compared to 0.5. (P.I. Ann
Hornschemeier)
The Chandra X-ray Observatory is providing data
that will, among other things, determine if the
X-ray to optical flux ratio is suppressed in
cluster galaxies, and allow one to construct an
X-ray luminosity function for such objects.
(P.I. Ann Hornschemeier)
The twin Keck telescopes are pursuing, via DEIMOS
on Keck II and LRIS on Keck I, redshifts (for
cluster membership) and line strength indices
(for ages and metallicities) for the faint
galaxies. Ultra Compact Dwarf galaxies are also
being hunted. (P.I. R. Brent Tully)
The worlds largest optical/near-IR telescope,
the Gran Telescopio Canarias (GTC) in the Spanish
Canary Islands, is now online. The instrument
EMIR will be used to obtain near-IR spectra.
(P.I. Marc Balcells)
The Subaru Telescope is providing deep, wide
field-of-view B, R, i and H? images. Ionised
hydrogen gas traces current star formation in
galaxies, and our survey has probed 100 times
fainter than previous work, enabling us to see
which galaxies are still under construction.
Deep broadband exposures will provide colours for
thousands of faint dwarf galaxies, allowing us to
probe their past star formation history. (P.I.
Yutaka Komiyama)
The Hubble Space Telescope in orbit, with mirror
cover open.
Two colour (F814W, F465W) image from a single ACS
pointing. The bright galaxy is NGC 4874. Many
dwarf galaxies and numerous globular clusters are
also clearly visible.

• Scientific objectives of the HST/ACS Treasury
  Program include the following.
• To measure the relative abundances of bright and
  faint galaxies, down to MV -9 mag.
• To study globular star clusters associated with
  bright and faint galaxies, and learn what they
  can tell us about galaxy evolution.
• To study the structure and morphology of
  galaxies, and to compare the various galaxy
  scaling laws with hierarchical and evolutionary
  models of galaxy formation.
• To quantify the physical properties of the
  nuclear star clusters which are prevalent in
  dwarf galaxies and explore the connection with,
  and possibly transition to, supermassive black
  holes.
• To provide accurate measurements of the sizes of
  the depleted stellar regions around supermassive
  black holes at the centres of giant galaxies,
  enabling one to constrain their dry merger
  history.
• To study the stellar populations from both
  global colours and radial colour gradients (F814W
  - F475W), and how the internal chemical evolution
  of galaxies is affected by interactions with the
  cluster environment.
• To establish an accurate 3D picture of the Coma
  cluster, via SBF measurements, and additionally
  examine the effect of the cluster environment
  upon the morphological features of galaxies (such
  as disks, bulges, bars and spiral arms) and
  compare these structures with those in field
  galaxy samples.
• To Identify dwarf galaxy samples, including
  ultra compact dwarfs, for further study with the
  new generation of multi-object spectrographs on
  8-10 metre class telescopes such as Keck, Subaru,
  Gemini and the GTC.

The 6.5 m Multi Mirror Telescope (MMT) is
providing, via Hectospec, galaxy redshifts along
with ages and chemical compositions. Some 7000
objects have been observed to date. (P.I. Ron
Marzke, Ann Hornschemeier Russell Smith)
The United Kingdom Infra-Red Telescope (UKIRT) is
providing wide field-of-view near-IR images.
Galaxies in dense cluster environments are
subject to various physical processes, yet
detailed studies of galaxy evolution to date have
tended to focus on large massive galaxies - those
least sensitive to environmental influence. We
are undertaking a near-IR imaging survey with the
Wide Field Camera (WFCAM) to cover 4x4 square
degrees around the centre of the Coma cluster,
probing down to the dwarf galaxy regime. Stellar
masses will also be obtained and compared with
dynamical masses. (P.I. Mustapha Mouchine)
The Very Large Array (VLA) in the USA has
obtained the deepest ever 20 cm map of the Coma
cluster. Radio emission from galaxies is a
signature of either accretion of material onto a
massive black hole or the formation of young
stars. In conjunction with the optical redshift
data, we will be able to construct the deepest
radio luminosity function ever derived for a
galaxy cluster. (P.I. Neal Miller)
The Canada-France-Hawaii Telescope (CFHT) will
provide deep near-infrared imaging to complement
the UKIRT data. (P.I. Mike Hudson)
The Coma Cluster Treasury Survey shall provide a
key local, high-density benchmark for comparison
to surveys of less dense galaxy environments
(e.g., the Virgo, Fornax and Perseus galaxy
clusters), high-redshift HST cluster surveys, and
field surveys such as HUDF, GOODS and GEMS.
Annual Astronomical Society of Australia Meeting,
Perth, July 2008