The rotation curve and geometry of M 31 at large galactocentric distances.

view Abstract Citations (218) References (18) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The rotation curve and geometry of M31 at large galactocentric distances. Roberts, M. S. ; Whitehurst, R. N. Abstract New 21-cm observations of the southern end of M3l indicate (1) that the plane of H I is bent away from the conventional plane by up to 5 kpc and (2) that the rotational velocity is essentially constant over the outer 10 kpc, i.e., from 20 to 30 kpc radius. The latter implies a mass that increases linearly with R over this range and a mass-to-luminosity ratio of > 200 for this outer region. At 30 kpc the surface density is 50 M0 pc-2. Dwarf M stars, the most common type of star in the solar vicinity, of number density of a few tenths pc - are adequate to explain the required mass and the mass-to-luminosity ratio. At these distances H I is 1 percent of the total mass. Subject headings: galaxies, individual - galaxies, motions in - galaxies, stellar content of - 21-cm radiation Publication: The Astrophysical Journal Pub Date: October 1975 DOI: 10.1086/153889 Bibcode: 1975ApJ...201..327R full text sources ADS | data products SIMBAD (1) NED (1)