Spatial Clustering from GALEX-SDSS Samples: Star Formation History and Large-Scale Clustering

Abstract

We measure the projected spatial correlation function w_p (r_p ) from a large sample combining Galaxy Evolution Explorer ultraviolet imaging with the Sloan Digital Sky Survey spectroscopic sample. We study the dependence of the clustering strength for samples selected on (NUV – r)_(abs) color, specific star formation rate (SSFR), and stellar mass. We find that there is a smooth transition in the clustering of galaxies as a function of this color from weak clustering among blue galaxies to stronger clustering for red galaxies. The clustering of galaxies within the "green valley" has an intermediate strength, and is consistent with that expected from galaxy groups. The results are robust to the correction for dust extinction. The comparison with simple analytical modeling suggests that the halo occupation number increases with older star formation epochs. When splitting according to SSFR, we find that the SSFR is a more sensitive tracer of environment than stellar mass.

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