The WIRCam Deep Survey II: Mass Selected Clustering

We present an analysis of the clustering of galaxies from z = 2 to the present dayusing the WIRCam Deep Survey (WIRDS). WIRDS combines deep optical data from the CFHTLSDeep fields with its own deep near-infrared data, providing a photometric data-set over aneffective area of 2.4 deg^2, from which accurate photometric redshifts and stellarmasses can be estimated. We use the data to calculate the angular correlation function forgalaxy samples split by star-formation activity, stellar mass and redshift. Using WIRDSwith its large total area and multiple fields gives a low cosmic variance contribution tothe error, which we estimate to be less than ~2.8%. Based on power-law fits, we estimate the real-space clusteringfor each sample, determining clustering lengths and power-law slopes. For galaxiesselected by constant mass, we find that the clustering scale shows no evolution up toz = 2.Splitting the galaxy sample by mass, we see a consistent trend for higher mass galaxies tohave larger clustering scales at all redshifts considered. We use our results to test thegalform semi-analytical model of galaxy formation and evolution. The observedtrends are well matched by the model galaxies for both the redshift evolution and the massdependence of the galaxy clustering. We split the galaxy population into passive andstar-forming populations based on rest-frame dust-corrected NUV-r colours. We find that thepassive galaxy populations show a significantly larger clustering scale at all redshiftsthan the star-forming population below masses of M_⋆ ~10^11 h^-1 M_⊙,showing that even at z =2 passive galaxies exist in denser environments than the bulk of thestar-forming galaxy population. For star-forming galaxies with stellar masses ofM_⋆ ≳10^11 h^-1 M_⊙,we find a clustering strength of ~8 h^-1 Mpc across all redshifts, comparableto the measurements for the passive population. Additionally, for star-forming galaxies wesee that clustering strength increases for higher stellar mass systems, however littlesign of a mass dependence in passive galaxies is observed over the range in stellar massthat is probed. Comparing our results to the model galaxy population produced bygalform, we find a qualitative good agreement between the model predictions andthe observed clustering. Finally, we investigate the connection between galaxy stellarmass and dark matter halo mass, showing a clear correlation between the two in both theWIRDS data and the galform predictions.

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15 pages, 10 figures, submitted to A&A

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