luminosity & color of galaxies in clusters

sarah m. hansenuniversity of chicago

witherin s. sheldon (nyu)

risa h. wechsler (stanford)

astrophysics with eV photons

sarah m. hansenuniversity of chicago

witherin s. sheldon (nyu)

risa h. wechsler (stanford)

sarah m. hansen glcw8

outline

motivation

sdss data & cluster sample characterizing the galaxy population

luminosity function: dependence on cluster mass, galaxy color

blue fraction: dependence on cluster mass, redshift, galaxy luminosity & cluster-centric radius

sarah m. hansen glcw8

motivation

clusters as cosmological probes how to connect dark and luminous matter? how to connect stars and gas?

clusters as galaxy evolution laboratories what’s happened to form such a particular cluster

galaxy population?

for upcoming large surveys, want to understand these details better

sarah m. hansen glcw8

sdss clusters > 7300 deg2 of ugriz

photometric data maxBCG clusters

red sequence matched filter (koester et al. 2007a,b)

z ≤ 0.3;z ~ 0.01 mass proxy: N200

mass - richness scaling mass function & cosmological

params (rozo et al. 2007) velocity dispersion

(becker et al. 2007) lensing (sheldon et al.;

johnston et al.) x-ray (rykoff et al.)

13,823 systems

with N200 ≥ 10

and z ≤ 0.3

sarah m. hansen glcw8

method

measure background-subtracted, k-corrected distribution of galaxies associated with clusters, binned by cluster & galaxy properties

• luminosity function as f (richness, color)

• blue fraction as f (richness, redshift, radius, luminosity)

galaxy properties

BCG or not?

radial distance

luminosity

color

cluster properties

richness

total luminosity

redshift

BCG properties

comparison with ADDGALs simulations (wechsler et al.)

sarah m. hansen glcw8

conditional luminosity function

(L|M): important ingredient for understanding how galaxies populate halos

sarah m. hansen glcw8

radial color trend is due to changing number of galaxies on the red sequence vs in the blue cloud

blue fraction is the info you need

color distribution

red galaxies; blue galaxies all galaxies

sarah m. hansen glcw8

blue fraction within r200

provides constraints on models of galaxy

populations and evolution in clusters

sarah m. hansen glcw8

blue fraction within r200

provides constraints on models of galaxy

populations and evolution in clusters

sarah m. hansen glcw8

blue fraction, in more detail

radial trend luminosity trend

sarah m. hansen glcw8

summary

blue fraction as a function of cluster mass, redshift, radius and magnitude

conditional luminosity function

for all, red & blue galaxies

with sdss data and galaxy-populated simulations, we investigate the properties of cluster galaxies, including:

see hansen et al., arXiv:0706.soon