CLUSTERING OF STAR-FORMING GALAXIES DETECTED IN MID-INFRARED WITH THE SPITZER WIDE-AREA SURVEY

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 = 0fdg01-3fdg5 , 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 r 0 = 4.98 ± 0.28 h -1 Mpc and r 0 = 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 >~ 3 × 1012 h -1 M sun, compared to M tot >~ 7 × 1011 h -1 M sun 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 sun, while the low-z subsample mainly consists of "LIRGs," L IR ~ 1011 L sun. 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.