The morphology of the ionized gas in M31's bulge

We present Hα + [N II] and B - λ6200 images of M31's bulge made by coadding hundreds of CCD frames taken over the past five years. Exceptional detail is seen in the images; among the most interesting features are an inner region of gas which appears more face-on than M31's optical disk, an almost circular arm of emission curving around the southern half of the bulge, and a series of emission threads extending over 500 pc in length. New CCD spectro- scopy of the [S II] lines λλ6716, 6731 reveals that the gas density falls off by at least two orders of magnitude in the central arcminute of the galaxy. These data, the observed gas kinematics, and the lack of a sizable ISM in M31's bulge argue strongly for the existence of a galactic wind in this region. The morphology of the ionized gas, the gas kinematics, and stellar kinematics all reveal a remarkable asymmetry in M31's bulge. The data suggest that the gas collected from stars in the bulge has collapsed into a disk whose plane is tipped relative to that of the stellar disk. This small inner gas disk itself appears to be warped such that the gas south of the nucleus is viewed closer to face-on than the gas in the northern half of the galaxy.