Evidence for Galaxy-Galaxy Interactions as an Active Agent of the ``Butcher-Oemler Effect'' at a Redshift of 0.2
Abstract
We present the spectra and images of 10 blue emission-line galaxies observed in Abell 963 (5), Abell 2111 (4), and Abell 2125 (1). We find a wide range in the spectral properties of the galaxies, yet the large majority of the galaxies has spectra which are consistent with very recent star formation. Only one of the 10 galaxies appears to contain an active nucleus. Since star formation is now occurring in these galaxies, residual effects from the triggering mechanism may still be apparent. Images of these emission-line galaxies show that several appear to be members of interacting systems. Others show evidence for possible interactions, either being somewhat morphologically disturbed or having disturbed neighbor galaxies. To test the idea of interactions, we performed a nearest neighbor analysis on these emission-line galaxies and a sample of red galaxies using the Kolmogorov-Smirnov test. The emission-line galaxies have closer neighbor galaxies than the red galaxy sample at greater than the 98% level of confidence. From this result and from the images themselves, we are lead to conclude that galaxy-galaxy interactions can induce "bursts" of star formation and are an active agent of the "Butcher-Oemler" effect at redshifts near 0.2. These interactions may be the primary cause of the "B-O" effect.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 1988
- DOI:
- 10.1086/166496
- Bibcode:
- 1988ApJ...330..596L
- Keywords:
-
- Galactic Clusters;
- Galactic Evolution;
- Interacting Galaxies;
- Emission Spectra;
- Interactions;
- Line Spectra;
- Red Shift;
- Star Formation;
- Astrophysics;
- GALAXIES: CLUSTERING;
- GALAXIES: EVOLUTION;
- GALAXIES: INTERACTIONS