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 shearKeck for membership and….

Treu et al. 2003; Moran et al. 2005 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• M200 = 6e14Msun

• R200=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. 2005 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. 2005R (Mpc) R (Mpc)

Bal

me

rO

II

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. 2006

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. 2006

0.04%

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