The ACS Coma Cluster Survey

Science TeamDave Carter (PI), Mustapha Mouhcine (LJMU) Harry Ferguson (US PI), Paul Goudfrooij, Bahram Mobasher, Thomas Puzia (STScI)John Lucey, Russell Smith, Ray Sharples (Durham) Neil Trentham (Cambridge); Jon Davies (Cardiff); Steve Phillipps (Bristol) Terry

Bridges (Queens, Kingston); Mike Hudson (Waterloo) David Merritt, Dan Batcheldor (Rochester) Shardha Jogee (Texas); RafaelGuzman (Florida); Brent Tully (Hawaii) Sadanori Okamura (Tokyo); Yutaka Komiyama (Subaru) Bianca Poggianti (Padova); Alister

Graham (ANU) Marc Balcells, Alfonso Aguerri (IAC); Peter Erwin (MPIE) Ann Hornschemeier (GSFC); Neal Miller (JHU) Bryan Miller(Gemini); Jennifer Lotz (NOAO) Reynier Peletier, Edwin Valentijn (Groningen) Ron Marzke (SFSU)

+ postdocs and students of the above, and some later additions

David Carter (Liverpool John Moores University) onbehalf of the Coma ACS survey team

Survey strategy• 82 ACS tiles (740 sq arcmin).

• Two regions at different galaxy and gaseous densities.

• Chosen for excellent coverage at X-ray (Chandra, XMM),Infra-red (Spitzer MIPS and IRAC), UV (Galex), Radio(VLA) wavelengths.

• Optical mosaic CCD photometry and redshifts fromoptical spectroscopy.

• Contiguous region in cluster core

• Targetted at known members in outer (infall) region.

• Two orbits per position

• F814W (4 x 350s) and F475W (4 x 640s) filters.

• 4 position (across the gap + subpixel) dither.

Science Goals

• Structure of dwarf galaxies–Luminosity function to MV ~ -9, comparison with other environments (Virgo, Fornax, Perseus, fieldsurveys).–Faint end of the global scaling laws, e.g. Fundamental Plane or equivalent.–Correlation of structure parameters e.g. Sersic index with absolute magnitude, mass.–Relationship between nucleii and galaxies - nuclear structure, nucleated dwarfs, ultra-compactdwarfs.

• Morphological components in a dense environment.–Disks and morphological transformations.–Bars in dense environments.–Nuclear dust rings and central star formation.

• Colours and colour gradients–Metallicity gradients produced in monilithic collapse models, diluted by subsequent mergers.–Recent star formation will lead to age gradients, leading to positive colour gradients (blue cores)–Colour gradients in galaxies with poststarburst spectra, spatial distribution of intermediate agepopulations.

• Properties of galaxies in clusters (comparison with Virgo/Fornax)–Globular clusters–Surface brightness fluctuations–Cores and central black holes

• Establishing the zero redshift baseline for studies of high redshift clusters.• Selection of samples from morphological criteria for faint spectroscopic study.

Data FlowProject Timescales•Data acquisition phase Nov 2006 - April 2008

– HST windows now over two cycles• Science exploitation phase - April 2007 - April 2009

– STScI and Groningen lead the data processingworkpackages– Science working groups being developed.– Annual project meetings.

• Outreach phase - April 2007 - April 2009– PI: Shardha Jogee, Texas.– Collaboration between Texas, STScI and JMU.– Radio programmes in English and Spanish– Coma images for online observatory and for museums.– High school level projects on the Coma cluster.– DVD on careers and research– Stardate Universo teachers guide update.

• Followup phase - June 2006 - Nov 2010– Multi-wavelength data (XMM, Chandra, Galex,Spitzer, VLA).– Near IR, near UV and Ha imaging (Subaru, CFHT,UKIRT).– Multi-object spectroscopy (Keck, Gemini, NOAO,WHT, Subaru)– HST/WFC3 further in the future.– Project leaders from the science team listed below.

Coma coreInfall region

Abstract: The ACS Coma Cluster survey is an HST Treasury programme (ID: GO10861)awarded 164 orbits in Cycle 15 to provide a comprehensive dataset on samples ofthousands of galaxies to MV ~ -9. In addition to the ACS dataset, the project will provide theimpetus for a variety of studies of the cluster with ground-based and space-basedobservatories, and at wavelengths from the X-ray to the radio. Data products will be readilyavailable to the wider community in MAST and Astro-Wise data archives.

Survey Requirements• Sufficient depth to probe to Mv = -8 for point sources• Detailed morphological data on a sample of galaxies toMv = -11• Probe a range of densities from the core to regions atwhich the density is 1 per ACS field.• Provide colour information.

Poster background by Thomas H. Puzia and Neal Miller, from originalimages from the Sloan Digital Sky Survey.

Estimated performance

Point source limiting magnitudes• For S/N = 10 in a 0.2 arcsec diameter aperture.• B = 27.3; V = 26.5 in F475W• I = 25.1in F814W

Limiting magnitudes for science goals• Limiting magnitude for galaxies surface brightnessdependent V~26 (MV ~ -9)• Basic structural parameters for sample selection (meansurface brightness, effective radius) to V ~ 23 (MV ~ -12).• Detailed structural parameters (Sersic index) to V ~ 21(MV ~ -14).• Colour gradients to V ~ 19.5 (MV ~ -15.5).

F475WF814W