Near-Nuclear Velocities in NGC 5907: Observations and Mass Models
Abstract
An optical spectrum of the edge-on Sc, NGC 5907, shows Hα, [N II], and [S II] emission to be double valued in the near-nuclear regions, 4" <= r <= 35". We attribute 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 Sackett 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 predicted from the outer rotation curve. However, all of these mass models of NGC 5907 are based on low-resolution HI observations with the innermost point at 60"; the models are a poor match to the new velocities. The forms and amplitudes of the mass components within NGC 5907 were previously poorly constrained due to the lack of velocities measured r <= 60". New mass models indicate that the mass-to-light (M/L) ratio of the bulge is smaller than previously determined. However, the disk M/L and halo parameters are still poorly constrained.
- Publication:
-
The Astronomical Journal
- Pub Date:
- December 1995
- DOI:
- 10.1086/117722
- Bibcode:
- 1995AJ....110.2692M
- Keywords:
-
- GALAXIES: INDIVIDUAL: NGC 5907;
- GALAXIES: NUCLEI;
- DARK MATTER