NEAR-NUCLEAR VELOCITIES IN NGC-5907 - OBSERVATIONS AND MASS MODELS

An optical spectrum of the edge-on Sc, NGC 5907, shows H alpha, [N II] , and [S II] emission to be double valued in the near-nuclear regions, 4 '' less than or equal to r less than or equal to 35 ''. We attribut e the higher velocity component to disk gas near the nucleus, and the lower velocity component to gas in the outer disk which is superposed along the line of sight. The galaxy recently acquired notoriety when S ackett et al. [Nature, 370, 441 (1994)] detected a luminous halo which falls off nearly as r(-2), close to the fall off for dark matter pred icted from the outer rotation curve. However, all of these mass models of NGC 5907 are based on low-resolution HI observations with the inne rmost point at 60 ''; the models are a poor match to the new velocitie s. The forms and amplitudes of the mass component within NGC 5907 were previously poorly constrained due to the lack of velocities measured r less than or equal to 60 ''. New mass models indicate that the mass- to-light (M/L) ratio of the bulge is smaller than previously determine d. However, the disk, M/L and halo parameters are still poorly constra ined. (C) 1995 American Institute of Physics.