Kinematics of an ``E+A'' Galaxy in Abell 665 at Z = 0.18
Abstract
The first profiles of rotational velocity and velocity dispersion are presented of a blue "Butcher-Oemler" galaxy in an intermediate-redshift cluster, Abell 665, at z = 0.18. A deep, high spectral resolution spectrum shows that the galaxy rotates rapidly, with an observed rotation speed of 180 km s^-1^. A lower resolution spectrum clearly shows that the galaxy has two population components, a young component resembling an A star spectrum, and an old component resembling a K star spectrum. This galaxy is therefore similar to "E + A" galaxies discovered previously by Dressler & Gunn in intermediate-redshift clusters. The luminosity profiles and kinematics of the two components are quite similar. The younger component is possibly more extended, and may be rotating faster in the center. This blue galaxy shows a large residual from the Faber- Jackson relation for the red galaxies in the same cluster. If it were an ordinary elliptical, it would be too bright by 2.2 +/- 0.5 mag in the J band. This is much larger than can be explained by the contribution of the young component. The Tully-Fisher relation implies a much smaller discrepancy of 0.3 +/- 0.3 mag. All the data are consistent with the hypothesis that the E + A galaxy is a disk galaxy, which is evolving into a cluster spiral or an S0 galaxy with low star formation rate at z = 0. There appear to be many possible counterparts in a nearby rich cluster like Coma.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- April 1993
- DOI:
- 10.1086/186792
- Bibcode:
- 1993ApJ...407L...5F
- Keywords:
-
- Disk Galaxies;
- Galactic Clusters;
- Galactic Evolution;
- Galactic Rotation;
- Galactic Structure;
- Stellar Spectra;
- A Stars;
- Astronomical Photometry;
- Astronomical Spectroscopy;
- K Stars;
- Red Shift;
- Stellar Luminosity;
- Astrophysics;
- GALAXIES: EVOLUTION;
- GALAXIES: KINEMATICS AND DYNAMICS;
- GALAXIES: PHOTOMETRY