MUSE-ALMA Halos V: Physical properties and environment of z < 1.4 HI
  quasar absorbers
  We present results of the MUSE-ALMA Halos, an ongoing study of the
Circum-Galactic Medium (CGM) of low redshift galaxies (z < 1.4), currently
comprising 14 strong HI absorbers in five quasar fields. We detect 43 galaxies
associated with absorbers down to star formation rate (SFR) limits of 0.01-0.1
solar masses/yr, found within impact parameters (b) of 250 kpc from the quasar
sightline. Excluding the targeted absorbers, we report a high detection rate of
89 per cent and find that most absorption systems are associated with pairs or
groups of galaxies (three to eleven members). We note that galaxies with the
smallest impact parameters are not necessarily the closest to the absorbing gas
in velocity space. Using a multi-wavelength dataset (UVES/HIRES, HST, MUSE), we
combine metal and HI column densities, allowing for derivation of the lower
limits of neutral gas metallicity as well as emission line diagnostics (SFR,
metallicities) of the ionised gas in the galaxies. We find that groups of
associated galaxies follow the canonical relations of N(HI) -- b and W_r(2796)
-- b, defining a region in parameter space below which no absorbers are
detected. The metallicity of the ISM of associated galaxies, when measured, is
higher than the metallicity limits of the absorber. In summary, our findings
suggest that the physical properties of the CGM of complex group environments
would benefit from associating the kinematics of individual absorbing
components with each galaxy member.
