The COS Absorption Survey of Baryon Harbors: The Galaxy Database and Cross-Correlation Analysis of OVI Systems
Abstract
We describe the survey for galaxies in the fields surrounding 9 sightlines to far-UV bright, z~1 quasars that define the COS Absorption Survey of Baryon Harbors (CASBaH) program. The photometry and spectroscopy that comprise the dataset come from a mixture of public surveys (SDSS, DECaLS) and our dedicated efforts on private facilities (Keck, MMT, LBT). We report the redshifts and stellar masses for 5902 galaxies within ~10 comoving-Mpc (cMpc) of the sightlines with a median of z=0.28 and M* ~ 10(10.1) Msun. This dataset, publicly available as the CASBaH specDB, forms the basis of several recent and ongoing CASBaH analyses. Here, we perform a clustering analysis of the galaxy sample with itself (auto-correlation) and against the set of OVI absorption systems (cross-correlation) discovered in the CASBaH quasar spectra with column densities N(O+5) >= 10(13.5)/cm2. For each, we describe the measured clustering signal with a power-law correlation function xi(r) = (r/r0)(-gamma) and find that (r0,gamma) = (5.48 +/- 0.07 h100-1 Mpc, 1.33 +/- 0.04) for the auto-correlation and (6.00 +/- 1 h-1 Mpc, 1.25 +/- 0.18) for galaxy-OVI cross-correlation. We further estimate a bias factor of bgg = 1.3 +/- 0.1 from the galaxy-galaxy auto-correlation indicating the galaxies are hosted by halos with mass Mhalo ~ 10(12.1 +/- 0.05) Msun. Finally, we estimate an OVI-galaxy bias factor bOVI = 1.0 +/- 0.1 from the cross-correlation which is consistent with OVI absorbers being hosted by dark matter halos with typical mass Mhalo ~ 10(11) Msun. Future works with upcoming datasets (e.g., CGM2) will improve upon these results and will assess whether any of the detected OVI arises in the intergalactic medium.