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Galaxy Surveys @ OABo. “ The Galaxy Mass Assembly History: from 10k to 20k zCOSMOS ”. Lucia Pozzetti INAF Osservatorio Astronomico di Bologna. Mass-assembly downsizing. LP et al.+ 09. mass-dependent evolution of the number/mass density: Massive tail is present up to z=1.

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galaxy surveys @ oabo
Galaxy Surveys @ OABo

“The Galaxy Mass Assembly History:

from 10k to 20k zCOSMOS”

Lucia Pozzetti

INAF Osservatorio Astronomico di Bologna

mass assembly downsizing
Mass-assembly downsizing

LP et al.+ 09

mass-dependent evolution of the number/mass density:

Massive tail is present up to z=1.

Continuous evolution for intermediate/low-mass galaxies

Mass assembly is earlier in more massive galaxies

in contrast with hierarchical models

merging fractions vs sfh mass growth
MERGING FRACTIONS vs. SFH MASS GROWTH

Merging fraction to explain the evolution of the global MF

Merging fraction after accounting for mass growth evolution due to the SFH(M) to explain remaining differences in observed and evolved MFs.

stellar mass function by types
Stellar Mass Function by types

MFs by colors/morphologies:Red/E+Bulge(ETGs)vs.Blue/Sp+Irr (LTGs)

Trasformation of blue/active into red/passive galaxies

MFs by SSFR:

SSFR<10-10 vs. SSFR>10-10

evolution of lf of etgs

Cimatti et al. 06

(Scarlata et al. 07)

Evolution of LF of ETGs

Increase with cosmic time since z=1 of the number densities of intermediate-L ETGs.

Mass-assembly downsizing for ETGs

in contrast with hierarchical models by De Lucia et al. 2006

formation of stars constraints from present day etgs galaxies
Formation of stars constraints from present-day ETGs galaxies

Constraints on age/SFH from σ, Hβ, Mgb, <Fe>, stellar populations

Thomas et al. 2004

See also:

Bernardi et al. 98,03-04

Kuntschner et al. 02

Pipino & Matteucci 2004

+MANY others…..

See Schiavon et al. 2006

for a different view…

=> ETGs dominated by old stellar populations

=> More massive spheroids form earlier and faster

=> Formation time scales independent of environment

~1-2 Gyr younger in low density environments

=> Mass assembly almost completed around z~1

evolution of the mf of etgs
Evolution of the MF of ETGs

ETGsdefined using different criteria (colors, morphology, spectral features, SFR or an intersection of them)

Increase with cosmic time since z=1 of the number densities of intermediate-mass ETGs.

Mass-assembly downsizing for ETGs

in contrast with hierarchical models

e s0 galaxies hierarchical merging predictions
E/S0 galaxies: hierarchical merging predictions

“Millennium Simulation”

N-body + semi-analytic model (Springel et al. 2005)

Assembly redshift = redshift when 50%

of the final stellar mass is contained in a single object

More massive galaxies assemble later

The final assembly is reached at z<1 for the massive galaxies

De Lucia et al. 2005

M>1011 Msun M>4x109 Msun

Mass-assembly up-sizing for ETGs

in hierarchical models

b uilding redshift of etgs
Building redshift of ETGs

z-building = Redshift at which the number density decreases by a factor 2 from redshift zero

z-building increases with mass

in contrast with hierarchical models

sam prediction for etgs mfs
SAM prediction for ETGs MFs
  • Hierarchical models :
  • Underpredict of luminous/red/massive galaxies at high-z
  • Overpredict low-Luminosity/Masses galaxies at all redshifts
f rom 10k to 20k bright sample
From 10k to 20k bright sample
  • Better constraints :
  • on ETGs growth rate, merging fractions and quenching fractions
  • New Analysis:
  • - Derivation of total Mass (Mstar+Mgas) MFs
  • [using the inversion of Kennicutt-Schimdt relation to derive Mgas or gas content (M) (from HI) up to the redshift observed (as lower limit !?).
  • - Comparison with hierarchical barionic MFs and halo MFs
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