MgII absorption through intermediate redshift galaxies

Abstract

The current status and remaining questions of Mgii absorbers are reviewed with an eye toward new results incorporating high quality Hubble Space Telescope images of the absorbing galaxies. In the end, we find that our current picture of extended gaseous regions around galaxies at earlier epochs is in need of some revision; Mgii absorbing “halos” appear to be patchier and their geometry less regular than previously inferred. We also find that the so-called “weak” Mgii absorbers are associated with normal galaxies over a wide range of impact parameters, suggesting that this class of absorber does not strictly select low surface brightness, dwarf galaxies, or IGM material. We emphasize the need for a complete survey of the galaxies in quasar fields, and the importance of obtaining rotation curves of confirmed absorbing galaxies.