Halo Gas and Galaxy Disk Kinematics of a Volume-Limited Sample of MgII Absorption Selected Galaxies at z 0.1
Abstract
MgII absorption lines detected in the spectra of background quasars allow us to probe the cool metal-enriched halo gas associated with foreground galaxies. This technique allows us to directly study the complex halo gas which provides the fuel for star-forming disks. The dynamics of this gas is likely driven by one or more of the following physical processes: supernovae ejecta, stellar winds, minor mergers, and inflow via filaments or satellites. In an effort to gain an understanding of how halos are built and evolve in a cosmological context, we directly compare the MgII halo gas kinematics to the rotation velocities derived from emission/absorption lines of their host galaxies. Our volume-limited sample of 11 z=0.1 MgII absorption systems are associated with 13 galaxies located at projected distances of 12-90 kpc from the quasar line-of-sight. In half of our sample the MgII absorption reside to one side of the galaxy systemic velocity and aligns with one side of its rotation curve. In the remaining half, the absorption spans both sides of the galaxy systemic velocity, although the bulk of the MgII resides mostly to one side of the galaxy systemic velocity.
We find that extended disk-like rotation models fail to reproduce the MgII velocity spread in all but one case, implying additional dynamical processes (outflow/infall) must be invoked to explain the observed range of MgII absorption velocities. In addition, intrinsic host galaxy NaI and MgI absorption line ratios suggest that these galaxies do not host strong outflows, which is also consistent with their low star formation rates. These results provide strong evidence that the MgII absorbers are associated with the infalling gas which is fueling galaxy star formation.- Publication:
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American Astronomical Society Meeting Abstracts #217
- Pub Date:
- January 2011
- Bibcode:
- 2011AAS...21741205K