2012ApJ...751..126S

We discuss the clustering properties of galaxies with signs of ongoing star formation detected by the Spitzer Space Telescope at the 24 µm band in the SWIRE Lockman Hole field. The sample of mid-IR-selected galaxies includes ∼20,000 objects detected above a flux threshold of S_24 µm_= 310 µJy. We adopt optical/near-IR color selection criteria to split the sample into the lower-redshift and higher-redshift galaxy populations. We measure the angular correlation function on scales of θ = 0°.01-3°.5, from which, using the Limber inversion along with the redshift distribution established for similarly selected source populations in the GOODS fields (Rodighiero et al.), we obtain comoving correlation lengths of r₀= 4.98 ±0.28 h^–1 Mpc and r₀= 8.04±0.69 h^–1 Mpc for the low-z (z_mean = 0.7) and high-z (z_mean= 1.7) subsamples, respectively. Comparing these measurements with the correlation functions of dark matter (DM) halos identified in the Bolshoi cosmological simulation, we find that the high-redshift objects reside in progressively more massive halos reaching M_tot ≳ 3x10¹² h^–1 M_☉, compared to M_tot ≳ 7x10¹¹ h^–1 M_☉ for the low-redshift population. Approximate estimates of the IR luminosities based on the catalogs of 24 µm sources in the GOODS fields show that our high-z subsample represents a population of "distant ULIRGs" with L_IR > 10¹² L_☉, while the low-z subsample mainly consists of "LIRGs," L_IR∼ 10¹¹ L_☉. The comparison of number density of the 24 µm selected galaxies and of DM halos with derived minimum mass M_tot shows that only 20% of such halos may host star-forming galaxies.