| Authors Affiliation: | 1 Inter-University Centre for Astronomy & Astrophysics, Post Bag 04, Pune, India, 411007
2 Leiden Observatory, Niels Bohrweg 02, 2333 CA Leiden, Netherlands
3 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD, USA
4 Department of Astronomy & Astrophysics, The University of Chicago, Chicago, IL 60637, USA
5 Department of Astronomy, University of Michigan, 1085 S. University Ave, Ann Arbor, MI 48109, USA
6 Leibniz-Institute for Astrophysics Potsdam (AIP), An der Sternwarte 16, D-14482 Potsdam, Germany
7 Department of Physics, University of Milan Bicocca, Piazza della Scienza 3, 20126, Milano, Italy |
| Abstract : | We present a detailed study of gas and metals, traced by Lya and OVI, around low-redshift galaxies using absorption lines in background quasar spectra. Our galaxy survey with MUSE IFU (MUSEQuBES, around 16 bright background quasars), combined with the data from the literature, provides us with a sample of galaxy-quasar pairs with a large dynamic range of galaxy properties. Stacked Lya absorptions with ~5000 quasar-galaxy pairs and impact parameters (b) up to 3 Mpc provide insights into the boundary between the circumgalactic gas around galaxies and the large-scale structures. We find enhanced Lya absorption around low-mass galaxies outside the virial radius compared to their high-mass counterparts, which hints at the filamentary gas as the potential origin of this excess absorption. The line-of-sight profile of stacked Lya absorption in our work can be well explained by a simple galaxy-absorber two-point correlation function. The enhancement and depletion of Lya absorption inside the virial radius of star-forming galaxies and very massive galaxies (logM*~10), respectively, are also supported by the individual Voigt-decomposed Lya absorption studies around the homogeneous sample of MUSEQuBES galaxies. The individual absorption studies also provide insight into kinematically different circumgalactic gas around low-mass galaxies. The metals traced by individual OVI absorption around these galaxies suggest that the majority of OVI absorbers arise in the virialized halo of galaxies with logM*~9.5. However, we find a substantial fraction of OVI absorptions within the virial radius of low-mass (logM*<9) galaxies. The kinematics suggesting the gravitationally unbound nature of these OVI absorptions led us to speculate that these might be the remnants of hot outflows. Finally, stacking of OVI absorption for galaxies without associated OVI absorption revealed a diffused OVI halo outside the virial radius of low-mass galaxies with N(OVI) ≈ 10^13.2 cm^{-2}. |
