formation and evolution of early-type galaxies in clusters
DESCRIPTION
Formation and Evolution of Early-Type Galaxies in clusters. Yara Jaff é 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 - PowerPoint PPT PresentationTRANSCRIPT
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