Which haloes host Herschel-ATLAS galaxies in the local Universe?

Abstract

We measure the projected cross-correlation between low-redshift (z < 0.5) far-infrared selected galaxies in the science demonstration phase (SDP) field of the Herschel-ATLAS (H-ATLAS) survey and optically selected galaxies from the Galaxy and Mass Assembly (GAMA) redshift survey. In order to obtain robust correlation functions, we restrict the analysis to a subset of 969 out of 6900 H-ATLAS galaxies, which have reliable optical counterparts with r < 19.4 mag and well-determined spectroscopic redshifts. The overlap region between the two surveys is 12.6 deg2; the matched sample has a median redshift of z approximate to 0.2. The cross-correlation of GAMA and H-ATLAS galaxies within this region can be fitted by a power law, with correlation length r(0) approximate to 4.63 +/- 0.51 Mpc. Comparing with the corresponding autocorrelation function of GAMA galaxies within the SDP field yields a relative bias (averaged over 2-8 Mpc) of H-ATLAS and GAMA galaxies of b(H)/b(G) approximate to 0.6. Combined with clustering measurements from previous optical studies, this indicates that most of the low-redshift H-ATLAS sources are hosted by haloes with masses comparable to that of the Milky Way. The correlation function appears to depend on the 250-mu m luminosity, L-250, with bright (median luminosity nu L-250 similar to 1.6 x 1010 L-circle dot) objects being somewhat more strongly clustered than faint (nu L-250 similar to 4.0 x 109 L-circle dot) objects. This implies that galaxies with higher dust-obscured star formation rates are hosted by more massive haloes.