Noncircular gas velocities and the radial dependence of mass-to-light ratio in NGC 4594 (the Sombrero Galaxy)

Abstract

view Abstract Citations (51) References (42) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Noncircular Gas Velocities and the Radial Dependence of Mass-to-Light Ratio in NGC 4594 (The Sombrero Galaxy) Kormendy, John ; Westpfahl, David J. Abstract Optical emission-line rotation velocities are smaller than absorption-line velocities in the central 35" of NGC 4594 (the Sombrero galaxy). Therefore the gas is rotating at much less than circular velocity. Similar conclusions were reached by Fillmore, Boroson, and Dressler for other galaxies. This helps to explain an observation by Rubin and collaborators that very centrally concentrated galaxies sometimes have slowly rising H II rotation curves and unexpectedly small central mass-to-light ratios. In this sense, it is not proved that brightness distributions and rotation curves are inconsistent with each other and with constant mass-to-light ratio. The noncircular velocities in NGC 4594 may be connected with gas shed by bulge stars or with the X-ray halo. The mass distribution is calculated using absorption-line rotation velocities and velocity dispersions at r <= 35" and emission-line velocities at r > 35". The mass-to-light ratio is found to be nearly constant over a large range in radius (1" <~ r <~ 180"). The observations suggest that M/L_v_ increases by a factor of ~ 2 from 20" to 215" radius, but the mean value M/L_v_ = 2.5 +/- 0.5 and even the maximum value ~ 4 are normal for a bulge or elliptical galaxy of M_B_ = -22.03 (H_0_ = 50 km s^-1^ Mpc^-1^). Therefore there is no compelling evidence for halo dark matter inside r ~ 215". Publication: The Astrophysical Journal Pub Date: March 1989 DOI: 10.1086/167233 Bibcode: 1989ApJ...338..752K Keywords: Cosmic Gases; Mass To Light Ratios; Radial Velocity; Spiral Galaxies; Absorption Spectra; Brightness Distribution; Dark Matter; Elliptical Galaxies; Emission Spectra; Galactic Bulge; Astrophysics; GALAXIES: INDIVIDUAL NGC NUMBER: NGC 4594; GALAXIES: INTERNAL MOTIONS; GALAXIES: STELLAR CONTENT; GALAXIES: STRUCTURE; GALAXIES: X-RAYS full text sources ADS | data products SIMBAD (1) NED (1)