Models & ObservationsModels & Observationsgalaxy clustersgalaxy clusters

Gabriella De LuciaGabriella De Lucia

Max-Planck Institut für Max-Planck Institut für AstrophysikAstrophysik

Ringberg - October 28, 2005Ringberg - October 28, 2005

Outline:

Semi-analytic models -- substructures & galaxies -- hybrid models – methods, limits & aims -- applications

The ESO Distant Cluster Survey (EDisCS) -- the colour-magnitude relation -- cluster structure

Mathis H. et al., 2002

CDM CDM

The SAM – the hybrid models:

Halo galaxy

Central galaxy

Satellite galaxy

Springel et al. (2001)De Lucia et al., MNRAS, 2004

The SAM – the physics:

Hot Gas

Cold Gas

cooling

Ejected Gas

feedback

star formation

recycling

Stars

re-incorporation Metallicity dependenceMetallicity dependence(Sutherland & Dopita (Sutherland & Dopita 1993)1993)

It is important!! (Tissera It is important!! (Tissera &&Scannapieco 2003)Scannapieco 2003)DLG, Kauffmann & White, 2004DLG, Kauffmann & White, 2004

4 Mpc

DM density map

Cluster galaxies

A simulated cluster (M ~ 1015 M)

B-V > 0.8B-V < 0.8

Gabriella De Lucia, PhD ThesisGabriella De Lucia, PhD Thesis

Luminosity function

Colour-magnitude

Tully-Fisher

Metallicity-mass

Gas fraction-luminosity

DLG, Kauffmann & White, 2004DLG, Kauffmann & White, 2004

The field metalbudget

ej. slow wind slow

1+redshift

Mas

s me t

a ls /

Y *

Mst

ar

gas

starshot gas

ejected

retention ej. fast

Observational signature of differentfeedback models #2:

DLG, Kauffmann & White, 2004DLG, Kauffmann & White, 2004

Differences between different models become more dramatic at high redshifts

EDisCS clusters

White et al., A&A, in press

A wide range of masses and structural properties

The CM of 2 EDisCS clusters

53

spec. conf. members

single burst z=3exp. s.f.r. z=3

De Lucia et al., ApJL, 2004De Lucia et al., ApJL, 2004

deficitDe Propris et al.(2003)

V

Composite EDisCS @z=0.75

Coma

I-obs

V-rest

Num

ber o

f gal

axie

sThe red-sequence LF

Robust result – also present in the full photometric catalogue!

De Lucia et al., ApJL, 2004De Lucia et al., ApJL, 2004 (see also Kodama et al. 2004)

#lum

/#fa

int

redshift

ComaA496

EDisCS clusters There is a clear

increase in the luminous-to-faint ratio with increasing redshift

De Lucia et al., in prep.

The build-up of the CM relation

A “cosmic down-sizing” (Cowie, 1996). A problem for the hierarchical paradigm?

Ellipticals in our hierarchical model

Three channels to make bulges:In a ‘minor’ merger the stellar mass of the merged galaxy is transferred to the bulge of the central galaxies + burst of a fraction of the combined cold gas

A ‘major’ merger completely destroys the disc of the central galaxy + burst of a fraction of the remaining gas

Disk instability (Mo, Mao & White 1998)

1,031,049 (810,486 ) Es with Mstar > 4x109 (1x1010) Msun16% Es / 66% Sp / 18 % S0 (MV < -18)(13%, 67%, 20% Loveday et al., 1996)

AGN model for suppression of the cooling-flows (Croton et al., 2005)

De Lucia et al., astro-ph/0509725De Lucia et al., astro-ph/0509725

increasing Z

incr

easin

g ag

e

Brighter ellipticals are older AND more metal rich

The origin of the colour-magnitude

De Lucia et al., in preparationDe Lucia et al., in preparation

Gallazzi et al., in preparation

Elliptical galaxies also have a shorter formation timescale!This is “anti-hierarchical”!!!

The star formation histories: mass

De Lucia et al., De Lucia et al., astro-ph/0509725astro-ph/0509725

cluster ellipticals

field ellipticals

redshift

Lookback time (Gyr)

Mstar = 1012 Msun

Mstar = 109 Msun

clusters

field

1010M 1011M 1012M cluster

field

Lookback time (Gyr)

Lookback time (Gyr)

redshift

M200 = 1015 Msun

M200 = 1012 Msun

Elliptical galaxies in denser environment are older

The “double-downsizing” (see talk by T. Treu)

De Lucia et al., De Lucia et al., astro-ph/0509725astro-ph/0509725

A natural expectation in the hierarchical scenario

Ellipticals: formation & assembly

50 % stars formed

80 %

redshift

Frac

tion

of g

a lax

i es

50 % stars in a single object

80 %

redshift

De Lucia et al., astro-ph/0509725De Lucia et al., astro-ph/0509725

1 Mpc

Simulationz=0.398

cl1018-1211z=0.472

cl1216-1201z=0.795

Simulationz=0.783

1’

Simulated and real clusters

Full information about the spatial and redshift distribution of model galaxies

construction of simulated catalogues of galaxies including luminosity, colour, bulge-to-disc ratio etc.

Observing a simulated cluster

Model results can be treated with exactly the same methods used for the observational data

cl1216-1201 @ z= 0.8

a simulated cl @ z=0.8

Structure comparison

De Lucia et al., in preparationDe Lucia et al., in preparation

Conclusions: Semi-analytic models are a technique for studying galaxy

formation - they are not meant to be definitive! The ever more detailed picture of our Universe also requires

a more complex modelling

An apparent “down-sizing” in the formation of elliptical galaxies is not in contradiction with the hierarchical paradigm

A self-consistent approach that takes into account the spectro-photometric AND chemical evolution is necessary

Comparison with observational results (expecially at high redshifts) will provide important constraints on physical processes and missing physics.

CM of EDisCS clusters: a clear increase of the Lum/Faint ratio for passive red galaxies as a function of redshift