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M31 - a noticeably peculiar galaxy
Some of our correspondents more inclined towards physical/quantitative science may be interested in my recent posts in the thread
"M 31 repro"(by Marco) in the "Deep Space" forum, as regards the ring structures within M31 and the many peculiarities and non-planarities that exist in the morphology of the Andromeda Galaxy.
In this regard, I quote from Francois Schweizer in the symposium "Galaxies: Interactions and Induced Star Formation"(eds, Kennicutt, Schweizer, & Barnes) :
“Any large-field photograph of M31 shows not only the satellites M32 and NGC 205, but also the warped disk (e.g. Sandage 1961) and, when properly masked, the strikingly misaligned bulge. The misalignment against the major axis of the outer disk is of order 10 degrees (see Hodge 1992). “
This idea of a bulge misalignment is interesting, but the disk of M31 is so warped and bent in various places that there are several possible planes to measure the bulge misalignment from. Incidentally, I do have several examples in mind of specific edge-on disk galaxies in which the bulge component does appear to be at a noticeably different p.a. to the disk component.
On a related issue, I note that the strong tidal distortion of NGC 205 by M31 is well shown in Deep Space forum thread called "M110 - Satellite of the Andromeda Galaxy" by Leonardo70. There have been a few papers on this tidal distortion in the last 10 years, but modeling and observation are not very well advanced, as yet.
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