Presentation #427.01 in the session Intergalactic Medium, QSO Absorption Line Systems.
To sustain a steady rate of star formation in galaxies, gas must flow from the circumgalactic medium (CGM) onto galaxy disks. UV absorption line data from Project AMIGA has shown that the CGM of M31 is a significant reservoir of baryons, but the lack of detected, associated HI emission has made determining the metallicity, and hence the origin, of this gas impossible to date. We present a new 21-cm HI map of 17 square degrees of the inner CGM (R < 25 kpc) of M31 using the Robert C. Byrd Green Bank Telescope (GBT). Our new maps have a 5-σ sensitivity over a 20 km/s linewidth of N(HI)=5.125×1017 cm-2, making them the deepest to date of this area. We detected 13 previously discovered HVCs, 3 gas-rich satellite galaxies and at least 11 new HVCs associated with M31. Our data suggest that some of these HVCs may be interacting with the disk of M31.