The Cosmic Ultraviolet Baryon Survey (CUBS). II. Discovery of an H₂-bearing DLA in the Vicinity of an Early-type Galaxy at z = 0.576*

We report the serendipitous detection of an H$_{2}$-bearing damped Lyman-$\alpha$ absorber at z = 0.576 in spectrum QSO J0111-0316 Cosmic Ultraviolet Baryon Survey. Spectroscopic observations from HST-COS far-ultraviolet reveal a with log[N(HI)/cm^-2] 20.1 +/- 0.2 and log[N(H$_{2}$)/cm^-2] 18.97 (-0.06, +0.05). The diffuse molecular gas is found two velocity components separated by dv 60 km/s, >99.9% total H$_{2}$ column density concentrated one component. At metallicity $\approx$ 50% solar, there evidence for Fe enhancement dust depletion, dust-to-gas ratio $\kappa_{\text{O}} \approx$ 0.4. A galaxy redshift survey conducted IMACS LDSS-3C on Magellan reveals overdensity nine galaxies projected distance d <= 600 proper kpc (pkpc) line-of-sight offset dv$_{g}$ 300 km/s absorber. closest massive, early-type 41 pkpc which contains 70% stellar mass identified 310 close proximity to quiescent Fe-enhanced chemical abundance pattern suggest physical connection, contrast picture DLAs are primarily associated gas-rich dwarfs. This case study illustrates that deep surveys needed gain insight into diverse environments host dense potentially star-forming gas.