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 mu m band in the SWIRE Lockman Hole field. The sample of mid-IR-selected galaxies includes similar to 20,000 objects detected above a flux threshold of S-24 mu m = 310 mu Jy. 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 theta = 0 degrees.01-3 degrees.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 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 greater than or similar to 3 x 10(12) h(-1) M-circle dot, compared to M-tot greater than or similar to 7 x 10(11) h(-1) M-circle dot for the low-redshift population. Approximate estimates of the IR luminosities based on the catalogs of 24 mu m sources in the GOODS fields show that our high-z subsample represents a population of "distant ULIRGs" with L-IR > 10(12) L-circle dot, while the low-z subsample mainly consists of "LIRGs," L-IR similar to 10(11) L-circle dot. The comparison of number density of the 24 mu m selected galaxies and of DM halos with derived minimum mass M-tot shows that only 20% of such halos may host star-forming galaxies.