We present here results from a survey of intervening C iv absorbers at z < 0.16 conducted using 223 sightlines from the Hubble Spectroscopic Legacy Archive. Most systems ($83{{\ \rm per\ cent}}$) out of the total sample of 69 have simple kinematics with 1 or 2 C iv components. In the 22 C iv systems with well constrained H i column densities, the temperatures from the b-values imply predominantly photoionized plasma (T ≤ 105 K) and non-thermal dynamics. These systems also have solar or higher metallicities. We obtain a C iv line density of $d\mathcal {N}/dX = 5.1\pm 1.0$ for $\log [N(\rm {C}\, \small {{IV}})~(\rm {cm}^{-2})]\ge 12.9$, and $\Omega _{\rm {C}\, \small {{IV}}}=(8.01\pm 1.62) \times 10^{-8}$ for $12.9 \le \log [N(\rm {C}\, \small {{IV}})~(\rm {cm}^{-2})] \le 15.0$. The C iv bearing diffuse gas in the z < 0.16 Universe has a metallicity of (2.07  ±  0.43)  ×  10−3 Z⊙, an order of magnitude more than the metal abundances in the IGM at high redshifts (z ≳ 5), and consistent with the slow build-up of metals in the diffuse circum/intergalactic space with cosmic time. For z < 0.015 (complete above L > 0.01L⋆), the Sloan Digital Sky Survey provides a tentative evidence of declining covering fraction for strong C iv (N > 1013.5 cm−2) with ρ (impact parameter) and ρ/Rvir. However, the increase at high separations suggests that strong systems are not necessarily coincident with such galaxies. We also find that strong C iv absorption at z < 0.051 is not coincident with galaxy over-dense regions complete for L > 0.13L⋆.

We present analysis on three intervening Hi-Civ absorption systems tracing gas within galaxy group/cluster environments, identified in the HST/COS far-UV spectra of the background quasars PG 1148 + 549 (z abs = 0.00346), SBS 1122 + 594 (z abs = 0.00402) and RXJ 1230.8 + 0115 (z abs = 0.00574). The ionization models are consistent with the origin of metal lines and H i from a cool and diffuse photoionized gas phase with T 4 × 10 4 K and n H 5 × 10 −4 cm −3 . The three absorbers have 89, 51 and 17 galaxies detected within 1 Mpc and |∆v| < 600 km s −1 . The RXJ 1230.8 + 0115 sightline traces the outskirt regions of the Virgo cluster where the absorber is found to have supersolar metallicity. The detection of metal lines along with H i has enabled us to confirm the presence of cool, diffuse gas possibly enriched by outflows and tidal interactions in environments with significant galaxy density.

We study the shapes of spatially integrated $\rm{H}\, \small {{I}}$ emission line profiles of galaxies in the eagle simulation using three separate measures of the profile’s asymmetry. We show that the subset of eagle galaxies whose gas fractions and stellar masses are consistent with those in the xGASS survey also have similar $\rm{H}\, \small {{I}}$ line asymmetries. Central galaxies with symmetric $\rm{H}\, \small {{I}}$ line profiles typically correspond to rotationally supported $\rm{H}\, \small {{I}}$ and stellar disks, but those with asymmetric line profiles may or may not correspond to dispersion-dominated systems. Galaxies with symmetric $\rm{H}\, \small {{I}}$ emission lines are, on average, more gas rich than those with asymmetric lines, and also exhibit systematic differences in their specific star formation rates, suggesting that turbulence generated by stellar or AGN feedback may be one factor contributing to $\rm{H}\, \small {{I}}$ line asymmetry. The line asymmetry also correlates strongly with the dynamical state of a galaxy’s host dark matter halo: older, more relaxed haloes host more-symmetric galaxies than those hosted by unrelaxed ones. At fixed halo mass, asymmetric centrals tend to be surrounded by a larger number of massive subhaloes than their symmetric counterparts, and also experience higher rates of gas accretion and outflow. At fixed stellar mass, central galaxies have, on average, more symmetric $\rm{H}\, \small {{I}}$ emission lines than satellites; for the latter, ram pressure and tidal stripping are significant sources of asymmetry.