Formation and Evolution of Early-Type Galaxies in clusters

Formation and Evolution of Early-Type Galaxies in clusters

Yara Jaffé1,2

Alfonso AragÓn-Salamanca1

1. The University of Nottingham2. European Southern Observatory

MAGPOP08Paris, 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. 2006

z > 0: De Lucia et. al. 2007

Slope (m) Mass-metallicity relation

Scatter (δ) due to small changes in tF

Evolution of m and b E’s evolved passively since formation at high z:

SF history: THE PARAMETER

tAvailable time

tF(look-back time since

last episode of SF)

tH(total age of the Universe)

= Δt / (tH - tF)

ΔtSpread in

formation time

t=0

THE SCATTER-AGE TEST1. Measure the observed scatter (σ) from the CMR

2. Compute δint by subtracting the errors introduced from the photometry

3. Colour evolution for different values of β using:

4. Comparison with population synthesis models

THE DATAESO 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. 2005 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. 2008 HST imaging for the of the highest-z clusters (80 orbits) Desai et al. 2007 Narrow band Hα (3 clusters) and XMM data (3 clusters) Finn et al. 2005 and Johnson et al. 2006 respectively

Sub-set of 137 early type galaxies (selected by morphology) in 10 clusters

AIM:

To probe if the scatter or tF, 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...

1. Individual analysis (cluster by cluster)

2. Overall analysis (all the clusters together)

CMDs of the clustersCL 1216.8-1201z = 0.79Age at z = 6.87 Gyrs----------------------------

No. galaxies = 31δint = 0.065 ±

0.009

residuals

MODEL COMPARISON

Bruzual & Charlot 2003- SSP- 3 different metallicities- Chabrier's IMF- Low res. libraries- 0.1 Gyr of constant SF and then passive evol.- No dust attenuation

CL 1216.9-1201

d(R-I) / dtF

Zsub-solarZsolarZover-solar

R - I

tF (Gyr)

d(R-

I)/

dtF

DIFFERENT COLOURS (in CMDs)

All the early-type galaxies In CL 1216.8 1201 (z~0.8)

R-I I-J R-J V-I I-K V-J

U V

DIFFERENT COLOURS

β=1.0

β=0.3

β=0.1 ... tH(z)

SCATTER ANALYSIS

1. Individual analysis (cluster by cluster)

2. Overall analysis (all the clusters)

SUB-SAMPLES

All the galaxiesin all the clusters

Low σv High σvLow z High z

Es S0s Lum Faint

RESIDUAL DISTRIBUTIONδint=0.076-0.004

+0.005

( δint=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 .… tH(<z>)

= Δt / (tH - tF)

δint(rf U-V) δint(rf U-V)

t F (

Gyr

)t F

(G

yr)

PRELIMINARY CONCLUSIONS:• For CL 1216.8 1201 all the colours seem to give consistent tF (for β=0.3 and β=1.0) scatter about the CMR is due to age differences• The estimated tF 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