A wide field multi-wavelength survey of two clusters at z~0.5 Tommaso Treu (UCSB)

Collaborators O. Czoske (Bonn) A. Dressler (OCIW) R.S. Ellis (Caltech) J. Geach (Durham) P. Hudelot (Toulouse) J.-P. Kneib (Marseille) P.J. Marshall (Stanford) S.M. Moran (Caltech) P. Natarajan (Yale) A. Oemler (OCIW) R.M. Rich (UCLA) S. Salim (UCLA) I. Smail (Durham) G.P. Smith (Birmingham)

Motivations

“Hierarchical” evolution of the morphology-density relation Smith, Treu, Ellis, Moran & Dressler 2005 (also: Dressler et al 1997; Treu et al. 2003; Postman et al. 2005)

Downsizing and “Double Downsizing” “Double Downsizing”: star formation history depends on mass of the galaxy AND (more weakly) on mass of the structure Treu et al. 2005a,b

The importance of wide area Evidence for infall and trends in star formation rates (e.g. Abraham et al. 1996). What happens to the infalling galaxies when they encounter the cluster potential, ICM…? The periphery is a “clean region” (see next slide)

Proposed mechanisms. Can we find the “culprit”? Treu et al. 2003

Survey Design and Description

Sample Selection: the role of the ICM Cl0024 and MS0451 because: Redshift (z~0.5) appropriate for lensing and detailed studies; look-back time high enough for evolution Both clusters have strongly lensed features at the center for mass reconstruction Very different X-ray properties, different ICM? (TX=4 vs 8 kev; LX=5 vs 51 10^44 erg/s; Ettori et al.; Ota et al.; Mass ratio?)

HST for morphologies and shear Keck for membership and…. Treu et al. 2003; Moran et al Over 1300 redshifts (500 members) per cluster

… stellar kinematics and stellar population diagnostics Moran et al. 2005

Spitzer-MIPS 24 micron imaging for obscured star formation… 5x5 grid without the center (GTO), i.e. 25’x25’ per cluster (PI: Smail) 938s per pixel, 0.2 mJy at 24micron (5sigma) Sensitive to dust emission (obscured star formation) Geach, Smail et al. 2006

..and GALEX NUV imaging for recent star formation GALEX NUV (2500A; 1.2 diameter fov) observed for 15ks (CL0024) and 45ks (MS0451) in Cycle 1 (PI: Treu). Limit of NUV~24 AB. Detect star formation in the last 10^7-10^8 yrs CL0024

..and GALEX NUV imaging for recent star formation

Selected Results

Mass profile: normalization with strong lensing The presence of a multiply imaged background galaxy of known redshift provides an absolute normalization of the total enclosed mass within the Einstein Radius. Kneib et al. 2003

Mass Profile Mass profile determined from 200 kpc to 4 Mpc Mass follows light M 200 = 6e14M sun R 200 =1.8Mpc C=22 Mass-to-light ratio is constant: group infall? MASS: ISOTHERMAL MASS: NFW LIGHT Kneib et al. 2003

Mass Profile: how about the inner regions?

Mass Profile: how about the inner regions? II Beware of ellipticity! Sand et al. 2004; Bartelmann & Meneghetti 2004; Dalal & Keeton 2004

Mass Profile: how about the inner regions? III Meneghetti et al used simulated (highly elliptical) clusters)

E+S0s: radial trends in star formation history. I Moran et al. 2005

E+S0s: radial trends in star formation history. II Moran et al R (Mpc) Balmer OII

E+S0s: cluster induced bursts Starforming E+S0 around the virial radius Balmer strong E+S0 inside the virial radius, consistent with infall scenario Harassment or interaction with shocks in the ICM as possible mechanisms Moran et al. 2005

E+S0s: cluster induced bursts. GALEX view Abundance of NUV detected E/S0 consistent with moderate amounts of recent star formation 10^7-10^8 Gyrs inside the virial radius. Consistent with infall scenario and burst of starformation at ~ the virial radius Moran et al CL0024

Star formation in E+S0s: comparing the two clusters Comparative study of star formation history of E/S0 Work in progess (beware of selection effects!) shows evidence for more recent star formation in CL0024 Possible explanations include: –a)CL0024 is far from relaxed, more shocks in the ICM; –b)double downsizing (MS0451 is more massive) Moran et al % 7.8% 4%

Completing the census of star formation: first MIPS results Both clusters detected as MIPS overdensities Hundreds of sources detected per cluster (crossidentification under way; spectroscopy in a few days….) In CL0024 correlation with SFR from an Ha Survey (Kodama et al. 2004) shows that SFR can be significantly obscured (6x with MIPS!) Geach et al. 2006

The end...to be continued