Abstract and slides by speaker > Howk Chris

The Andromeda galaxy provides unique opportunities to study the structure of galaxies like our own Milky Way in great detail. I will report on the results from Project AMIGA (Absorption Maps In the Gas of Andromeda), which uses HST/COS ultraviolet spectroscopy of ~30 background AGNs projected within ~300 kpc of M31 to study the distribution of metals in its circumgalactic medium. Additional very deep 21-cm observations with the GBT constrain the presence of dense, cold gas about M31. We find an extremely high covering factor of metals in our data, with ~90% covering factor of Si III within 300 kpc. The absorption by low-ionization species is at a lower column density than seen in other galaxy-selected CGM studies. A nearly complete lack of 21-cm emission to log N(HI)~17.6 limits the covering factor of such high HI column densities to <5% over the same area. This is in contrast to, e.g., the COS-Halos sample at z~0.2, which has a covering factor higher by factors of 2-3 for comparable impact parameters. I will discuss the implications of these results for the mass of the CGM about Andromeda and the nature of the diffuse CGM about galaxies more generally.