An Extended Hot Halo Gas Around M31

Our nearest spiral galaxy neighbor, M31, has diffuse bulge emission and probablyhas an extended diffuse halo of hot gas, similar to that seen in other spiralgalaxies. Unlike more distant spirals, where halo gas observations arephotonstarved, a M31 halo will not suffer this problem, allowing the gasdistribution to be measured and the temperature to be mapped with unprecedentedaccuracy. This will define halo gas properties, the diskhalo interface and itwill be a powerful test of models. This Xray halo can have a radial extent of 1degree (1015 kpc), so a mosaic of observations will be constructed along theminor axis, leveraging existing observations. By using overlapping fields, wewill flatfield the data to the necessary precision. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]