The COS Absorption Survey of Baryon Harbors: The Galaxy Database and Cross-correlation Analysis of O vi Systems

We describe the survey for galaxies in the fields surrounding nine 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 data set 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 of the sightlines with a median of z̄ = 0.28 and M̄_∗ 10^10.1M_⊙. This data set, 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 O vi absorption systems (cross-correlation) discovered in the CASBaH quasar spectra with column densities N(O⁺⁵) 10^13.5 cm^-2. For each, we describe the measured clustering signal with a power-law correlation function σ (r) = (r/r₀)^-γ and find that (r₀, γ )=(5.48\pm 0.07 h₁₀₀ ^-1 Mpc, 1.33 ± 0.04) for the auto-correlation and (6.00_-0.77 ^+1.09 h₁₀₀ ^-1 Mpc 1.25 ± 0.18) for galaxy-O vi cross-correlation. We further estimate a bias factor of b_gg =1.3 ± 0.1 from the galaxy-galaxy auto-correlation, indicating the galaxies are hosted by halos with mass M_halo ≈ 10^{12.1 ± 0.05} M_⊙. Finally, we estimate an O vi-galaxy bias factor b_{O VI} = 1.0 ± 0.1 from the cross-correlation which is consistent with O vi absorbers being hosted by dark matter halos with typical mass M_halo ≈ 10¹¹ M_⊙. Future works with upcoming data sets (e.g., CGM²) will improve upon these results and will assess whether any of the detected O vi arises in the intergalactic medium.