| Abstract | The edge-on, S0(+) galaxy NGC 5084 has been observed with the VLA telescope in the 21-cm line of atomic hydrogen. The resulting maps have an angular resolution of about 34 arcsec and a velocity resolution of about 51 km/s. The gas is found to be in a flat annulus containing some structure. The radial width of the annulus is comparable to its inner radius. Closely associated with the H I is a very faint optical disk containing some clumpy structure in its outer parts and a weak dust lane in the inner one-third of its extent. The galaxy is very massive, exceeding 10 to the 12th solar masses. It has an exceptionally large mass-to-light ratio, greater than or equal to 65 solar masses/solar-blue luminosities, and, for its type, an unusually high ratio of H I mass to blue luminosity approximately equal to 0.35 solar units. Relative to 'normal' galaxies of its mass and type, NGC 5048 appears to be underluminous by about 2 mag. The galaxy seems to be an extreme member of a class of massive, H I-rich, early-type disk galaxies. The symmetry axes of the inner lens and the H I disk coincide accurately. It is therefore most unlikely that the atomic hydrogen has been acquired by accretion. |
