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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)
“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)
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
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
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? 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: 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