Kavli Affiliate: Luis C. Ho
| First 5 Authors: Reena Chaudhary, Reena Chaudhary, , ,
| Summary:
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 $0.3 le z le 1.6$. Using nebular [O II]
$lambdalambda$3727,3729 emission lines identified in DESI fiber spectra
centered on quasar, we detect 377 galaxies at a typical detection rate of
$sim$0.45% at $z lesssim 1$, which increases with MgII equivalent width
($W_2796$). A significant fraction (74%) of these galaxies are associated
with strong absorbers with $W_2796 ge$ 2rA. These absorbers trace
galaxies spanning stellar masses of $rm 8.4 le log(M_star/M_odot) le
11.6$ and star formation rates (SFRs) of $rm -1.2 le
log(SFR~[M_odotyr^-1]) le 2.7$, located at projected galactocentric
distances of 4-24 kpc. We find the average MgII absorber strength increases
from 2.1rA to 2.9rA between redshifts $z sim$ 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 $W_2796$ versus $M_star$, 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.
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