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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
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