Jr. Ford W. Kent

Optical properties and dynamics of galaxies in the Hickson compact groups

Broad-band R images, Hα images, and Hα long-slit spectroscopy for a set of galaxies in 21 Hickson compact groups are presented. Some of the galaxies are tidally interacting and distorted; some appear morphologically normal. Observed velocity patterns range from too peculiar to form rotation curves (one-third of spiral sample), to abnormal (one-third), to normal (one-third); peculiar rotation curves are only loosely coupled with peculiar morphology. For individual galaxies, values of integral M/L B are low, slightly lower than for field spirals of equivalent Hubble type. All of these observations support a model in which the compact group galaxies have only recently accumulated from the lumpy general galaxy distribution, and which tidal interactions are frequent and ongoing.

One galaxy from several - The Hickson compact group H31

The compact group H31 was identified by Hickson in 1982; it consists of four galaxies in close proximity, at least two of which (A and C) are interacting. Red and H-alpha frames and long-slit spectroscopy identify at least three other close members of the group; an H I envelope encloses all galaxies. Nuclear spectra of galaxies A and C show velocity patterns characteristic of interacting galaxies as well as the broad 4650 A feature indicative of W-R stars. These features reveal that large numbers of massive stars formed more than 10 exp 6.5 yr ago. Other observed characteristics all suggest that H31 is in the process of merging to a single galaxy. H31 thus supports computations which indicate that galaxies in compact groups merge to form a single remnant. 52 refs.

The structure and evolution of Hoag's object

New imaging, photometric, and spectroscopic observations of Hoags object, a 16th magnitude galaxy consisting of an almost perfectly round core surrounded by a faint, apparently detached ring is presented. The observations and reduction procedures are addressed, and the physical properties of the galaxy and of its components are described, including the velocities, brightness profile, kinematics, and gas content. Old hypotheses about Hoags object are reviewed, and a new one is proposed in which the object owes its structure to an accretion event some time ago. 46 references.

Stellar Motions Near the Nucleus of M31

Velocities of stars along the major and minor axes in the nuclear bulge of M31 were measured from the lambda 5269 Fraunhofer E absorption line (Fe I + Ca I). The mean uncertainty of each velocity was estimated to be 25 km s/sup -1/. In general, the stellar velocities resembled the gas velocities reported earlier. Along the major axis, the velocities rose steeply across the nucleus, and showed a minimum at R = 1600 pc. Along the far minor axis, 300 pc < R < 800 pc, excess positive velocities were observed in those regions where gas was observed to be streaming out from the nucleus. These regions of anomalous velocities appeared to be coincident with spiral features. However, no realistic explanation of the complex stellar motions, or of their relation to the presumably younger gas, can be offered. (auth)