Formation and Evolution of Early-Type Galaxies in clusters Yara Jaffé 1,2 Alfonso Arag Ó n-Salamanca 1 1. The University of Nottingham 2. European Southern Observatory MAGPOP08 Paris, 12 Nov. 2008

OUTLINE - Introduction - Scatter-age test - The data - Some results - Conclusions

The CMD of galaxies in clusters

Universality of the CMR z = 0: Visvanathan & Sandage 1977 z = 0: Bower, Lucey & Ellis 1992 z > 0: Mei et. al z > 0: De Lucia et. al  Slope (m) Mass-metallicity relation  Scatter (δ) due to small changes in t F Evolution of m and b  E’s evolved passively since formation at high z:

SF history : THE  PARAMETER Available time t F (look-back time since last episode of SF) t H (total age of the Universe)  = Δ t / (t H - t F ) Δt Spread in formation time t=0

THE SCATTER-AGE TEST 1. Measure the observed scatter (σ) from the CMR 2. Compute δ int by subtracting the errors introduced from the photometry 3. Colour evolution for different values of β using: 4. Comparison with population synthesis models

THE DATA ESO Distant Clusters Survey (EDisCS) Detailed follow-up of 20 clusters from LCDCS (Gonzalez et al. 2001) at 0.4 < z < 1 Each field containing a main cluster and some other secondary clusters and groups

EDisCS Deep optical photometry from VLT (14 nights) White et al Near-IR photometry from NTT (20 nights) Aragon-Salamanca et al., in preparation Multi-object spectroscopy with FORS2/VLT (25 nights) Halliday et al. 2004; Milvang-Jensen et al HST imaging for the of the highest-z clusters (80 orbits) Desai et al Narrow band Hα (3 clusters) and XMM data (3 clusters) Finn et al and Johnson et al respectively Sub-set of 137 early type galaxies (selected by morphology) in 10 clusters

AIM: To probe if the scatter or t F, for a fixed value of β, depend on: The morphological sample (E´s vs. S0´s) The cut in Luminosity (mass) The colour chosen in the CMDs Properties of the clusters ?

SOME RESULTS Individual analysis (cluster by cluster) 2. Overall analysis (all the clusters together)

CMDs of the clusters CL z = 0.79 Age at z = 6.87 Gyrs No. galaxies = 31 δ int = ± residuals

MODEL COMPARISON Bruzual & Charlot SSP - 3 different metallicities - Chabrier's IMF - Low res. libraries Gyr of constant SF and then passive evol. - No dust attenuation CL d(R-I) / dt F Z sub-solar Z solar Z over-solar R - I t F (Gyr) d(R-I)/dt F

DIFFERENT COLOURS (in CMDs) All the early-type galaxies In CL (z~0.8) R-II-JR-JV-II-KV-J U V

DIFFERENT COLOURS β=1.0 β=0.3 β= t H (z)

SCATTER ANALYSIS 1. Individual analysis (cluster by cluster) 2. Overall analysis (all the clusters)

SUB-SAMPLES All the galaxies in all the clusters Low σ v High σ v Low zHigh z EsS0sLumFaint

RESIDUAL DISTRIBUTION δ int = ( δ int =0.063 )

All the sample: β=1.0  Δt (rf U-V) ~ 1.7 Gyr β=0.3  Δt (rf U-V) ~ 1.0 Gyr β=0.1  Δt (rf U-V) ~ 0.5 Gyr.… t H ( )  = Δ t / (t H - t F ) δ int (rf U-V) t F (Gyr)

PRELIMINARY CONCLUSIONS: For CL all the colours seem to give consistent t F (for β=0.3 and β=1.0)  scatter about the CMR is due to age differences The estimated t F doesn’t seem to change much (within errors) with galaxy luminosity (mass), morphology or cluster propperties (vel. disp and z) but some trends are found