Clustering of galaxies at 3 . 6 microns in the Spitzer Wide-area Infrared Extragalactic legacy survey
Waddington, I ; Oliver, S J ; Babbedge, T S R ; et al. ; - ASI Sponsor
Jan - 2007

journal : Mon.Not.Roy.Astron.Soc
type: Article Journal

Abstract
We investigate the clustering of galaxies selected in the 3. 6 \mu m band of the Spitzer Wide-area Infrared Extragalactic (SWIRE) legacy survey. The angular two-point correlation function is calculated for eleven samples with flux limits of S 3 . 6 > 4 –400 \mu Jy, over an 8 square degree field. The angular clustering strength is measured at > 5 - \sigma significance at all flux limits, with amplitudes of A = (0 . 49 – 29) × 10 − 3 at one degree, for a power-law model, A\theta − 0 . 8 . We estimate the redshift distributions of the samples using ph enomological models, simulations and photometric redshifts, and so derive the spatial correl ation lengths. We compare our re- sults with the GalICS (Galaxies In Cosmological Simulation s) models of galaxy evolution and with parameterized models of clustering evolution. The GalICS simulations are consis- tent with our angular correlation functions, but fail to mat ch the spatial clustering inferred from the phenomological models or the photometric redshift s. We find that the uncertainties in the redshift distributions of our samples dominate the st atistical errors in our estimates of the spatial clustering. At low redshifts (median z 6 0 . 5 ) the comoving correlation length is approximately constant, r 0 = 6 . 1 ± 0 . 5 h − 1 Mpc, and then decreases with increasing redshift to a value of 2 . 9 ± 0 . 3 h − 1 Mpc for the faintest sample, for which the median redshift is z ∼ 1 . We suggest that this trend can be attributed to a decrease in t he average galaxy and halo mass in the fainter flux-limited samples, corresponding to chang es in the relative numbers of early- and late-type galaxies. However, we cannot rule out strong e volution of the correlation length over 0 . 5 < z < 1

keywords : axies – large-scale struc-,evolution,galaxies,galaxies: evolution – galaxies: statistics – infra,large-scale structure of universe,statistics,ture of universe