Dynamics of Warped Galaxies
نویسنده
چکیده
The HI gas in the outer regions of spiral galaxies commonly rises above and below the inner galactic plane in characteristic `integral sign' warps. Such bending distortions were rst observed nearly 40 years ago in our own galaxy (Burke 1957, Kerr 1957; see Burton 1988 for a review), and since then the nature and excitation of warped discs has been a major unsolved problem in galactic dynamics (Binney 1992). Interest in warped galaxies has increased with the recognition that they are quite common: all three spiral galaxies in the Local Group are warped, and most edge-on disc galaxies appear to be warped to some extent (S anchez-Saavedra et al. 1990, Bosma 1991). The high frequency of warps implies that they are either long-lived or repeatedly excited.
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