1. Galaxy Populations in the Most Distant Clusters
Piero Rosati (ESO)
Collaborators
V.Strazzullo (ESO)
R.Demarco (JHU)
M.Nonino (Trieste) C.Lidman (ESO)
A.Rettura (ESO)
A.Stanford (LLNL)
P.Eisenhardt (JPL)
…and the ACS GTO Science Team (H.Ford, Postman, Blakeslee et al.)
Ringberg,

2. Motivation & Plan
Studies of clusters at z>1 provide the strongest constraints on formation scenario of cluster galaxy populations
Multiwavelength data sets - HST/ACS, VLT/ISAAC, Spitzer/IRAC - are needed to sample optical and near-IR restframe properties
part of the “ACS intermediate-redshift cluster program”
Measuring differences in properties between field and cluster galaxies provide a critical test for hierarchical formation models (easier at z>1!) (zF for gals of a given mass should depend on environment)
Tools:
Color-magnitude diagrams with HST/ACS and VLT/ISAAC
Stellar masses and ages from SED fitting of 9 passband photometry + composite spectra

3. FORS B + ACS z + ISAAC Ks RDCS1252.9-2927 at z=1.237
Mosaic of 4 ACS pointings, total of 20 orbits in z band, 12 orbits in i band combined with deep ISAAC imaging 38 spec members from VLT/FORS2
FORS B + ACS z + ISAAC Ks

4. Some cluster members in RDCS1252-29 with HST/ACS
Early-type spectra
BzK 5”
Late-type spectra
AGN-2

5. RDCS1252 (z = 1.24) C-M Relation with HST/ACS and VLT/ISAAC (Blakeslee et al. 03; Lidman et al. 03; Rosati et al . 04)
Lidman et al. 2004
Kodama&Arimoto 97 models
ZF= 2,3,5
VLT/ISAAC
Coma at z=1.24
HST/ACS E S0
Late
The scatter and slope of the red sequence is very similar to low-z clusters, basically frozen over 65% of look-back times !

6. RDCS0910 (z=1.10) - HST/ACS I & z bands
+ Chandra overlay

7. RDCS0910 (z = 1.105) C-M Relation with HST/ACS (Mei et al. 2005a)
S0 red.seq S0

8. C-M Relation of Lynx clusters (z = 1.27) (Mei et al. 2005b)
Lynx E (z=1.26)
Lynx W (z=1.27)

9. Lynx (z = 1.26, 1.27) C-M Relation with HST/ACS (Mei et al. 2005b)
Coma

10. (no) Evolution of the CMD slope and scatter out to z=1.3
Bower et al. 92
Ellis et al. 97
Stanford et al. 97
Van Dokkum et al. 01
Blakeslee et al. 03
Mei et al. 05a, b
(Mei et al. 05b)

11. Measuring stellar masses Comparing Dynamical & Photometric Masses at high redshift
Log(Mphot)
Log(Mdyn)
Dynamical masses for 51 galaxies at z= are available in GOODS/CDFS and RDCS1252 fields (van der Wel+ 05, di Serego Alighieri+ 05)
Excellent multi-wavelength coverage in both fields (9 bands from B through 3.6) allows accurate SED fitting up to K rest-frame: VLT/FORS HST/ACS VLT/ISAAC Spitzer/IRAC
Compare dynamical and stellar masses at z~1, with the bonus of morphological information
Stellar Pop models: BC03, Pegase
Rettura et al. (2005)

12. Age & Masses: 1252 (vs field)

13. Color-(Stellar)Mass Diagram at z=1.24

14. Stellar Mass segregation in RDCS1252

15. Composite spectrum of 10 brightest members at <z> = 1
Composite spectrum of 10 brightest members at <z> = (Rosati, Demarco 03)
Stacked spectrum of field galaxies (K20) at similar redshifts does not show prominent Hd abs line
Local Ell
> Significant Hd abs line
Last z=
Complex SF history needed to fit both SED and Spectrum
K20 Ell stack z~1
Cluster Ell stack
z=1.24

16. XMMJ 2235-25 at z=1.4 (Mullis et al. 2005)
Most distant X-ray luminous cluster known to date
~0.5 Gyr beyond Lynx clusters (z=1.27)
~1 Gyr beyond RDCS0910 (z=1.1)

17. Cluster red-sequence at z=1.4 from ISAAC observations
(Kodama&Arimoto 97 models)
Again: stellar populations appear ~3 Gyr old, i.e. zF~-4 (progenitor bias?)
Is the slope getting flat ?? (must wait for careful HST analysis…)

18. Evolution of distant ACS clusters in i-z vs J-Ks and comparison with CSP (KA97) tracks
1.24
1.27
z=1.4
RXJ0152
MS1054
z=0.83
At z>1 the CMD does not appear to be universal, clusters might take different evolutionary tracks..

19. Conclusions
Clusters and their galaxy populations were already in an advanced evolutionary state by z=1.4 (passive evol over 9 Gyrs) - considered heretic only 7 yrs ago…
Analyses of colors of massive cluster galaxies at increasing redshifts (at z>1) indicate that formation histories might be different (as expected but it’s nice to see it)..
Mass distributions in a range of environmental densities are similar at z~1 (exception of cluster cores) (see Strazzullo’s talk)
No apparent color-sequence in proto-clusters at z>2 (Miley et al.), are 2 Gyrs (~2 cluster crossing times) enough to build up a tight color sequence by z= ? - We have a good chance of observing the onset of the morphology-density relation at z<~2 in the near future