Spatial distribution of the starbursts in post-starburst coma cluster galaxies

We present long-slit spectra and multicolor CCD images which demonstrate that the strong star formation episodes that occurred in the post-starburst galaxies in the Coma Cluster and two field galaxies were not restricted to the central regions of the galaxies. Rather, the remnant young stars from the starbursts are found to be distributed over a large radius, though changes in the relative strength of the old and young components with radius are evident in a few cases. The Coma galaxies are shown to have exponential disk profiles, and the spectra provide further kinematical evidence that the galaxies are rotating systems, indicating that the galaxies are not ellipticals. The starburst material also appears to be distributed in disks. Such information places constraints on models for the starbursts that involve mergers. Population models are discussed in a companion paper, which show that the post-starburst spectra in these particular galaxies can not be reproduced by normal spiral-like star formation which simply ceased, but rather are due to a burst of star formation which ceased similar to 1 Gyr ago and which presently account for similar to 60% of the light at 4000 Angstrom. Curiously, an on-going starburst galaxy, previously identified in Caldwell er al. [AJ, 106, 413 (1993)] and also observed here, has its vigorous star formation isolated to its bulge region. The associated ionized gas shows peculiar kinematics, when compared to the gas located in the disk. Of four other Coma early-type galaxies with ionized gas studied here, two are shown to have emission spectra characteristic of active galactic nuclei, while two have spectra showing a mixture of HII region and AGN spectra. (C) 1996 American Astronomical Society