2025/09/02 by Chaudhary, Reena, Joshi, Ravi, Das, Sarbeswar +5
#Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences
paper · doi:10.48550/arxiv.2509.02672
We investigate the origin of intervening cool MgII absorption detected in the spectra of background quasars and the nature of associated galaxies across a broad redshift range of 0.3 ≤ z ≤ 1.6. Using nebular [O II] λλ3727,3729 emission lines identified in DESI fiber spectra centered on quasar, we detect 377 galaxies at a typical detection rate of ∼0.45% at z \lesssim 1, which increases with MgII equivalent width (W2796). A significant fraction (74%) of these galaxies are associated with strong absorbers with W2796 ≥ 2Å. These absorbers trace galaxies spanning stellar masses of \rm 8.4 ≤ log(M⋆/M\odot) ≤ 11.6 and star formation rates (SFRs) of \rm -1.2 ≤ log(SFR~[M\odotyr-1]) ≤ 2.7, located at projected galactocentric distances of 4-24 kpc. We find the average MgII absorber strength increases from 2.1Å to 2.9Å between redshifts z ∼ 0.4 and 1.2, indicating evolution in the cool gas content of galaxy halos. The relatively constant absorber strength with galactocentric distance implies a clumpy structure of cool gas in the circumgalactic medium (CGM). Further, we find a positive correlation between W2796 versus M_⋆, and SFR, suggesting that the distribution of metal-enriched cool gas in the CGM is closely tied to the properties of the host galaxies. The redshift evolution of gas-phase metallicity suggests that strong MgII absorbers trace the general population of star-forming galaxies. The velocity dispersion of the cool gas increases with halo mass, and the wide range of line of sight velocity offset (-389 to 364 \rm km s-1) between the galaxy systemic velocity and absorbers highlights the dynamical nature of CGM. However, the majority of this gas remains gravitationally bound to the dark matter halos, consistent with a picture of gas recycling via galactic fountains.