Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 2003
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003aas...203.2602g&link_type=abstract
American Astronomical Society Meeting 203, #26.02; Bulletin of the American Astronomical Society, Vol. 35, p.1249
Astronomy and Astrophysics
Astronomy
2
Scientific paper
E+A galaxies are characterized as a galaxy with strong Balmer absorption lines but without any [OII] or Hα emission lines. The existence of strong Balmer absorption lines means that E+A galaxies have experienced starburst within recent one Gyr. However, the lack of [OII] nor Hα emission lines indicates that E+A galaxies do not have any on-going star formation. Therefore, E+A galaxies are interpreted as a post-starburst galaxy. In this work, we pursue the origin of E+A galaxies using one of the largest samples of 133 E+A galaxies selected from the Sloan Digital Sky Survey data. We tested three popular explanations for E+A galaxies; (i) cluster-related phenomena (e.g., ram-pressure stripping) (ii) galaxy-galaxy merger/interaction (iii) dust enshrouded star formation. By studying the environment of E+A galaxies as a function of local galaxy density, we found many E+A galaxies in the rarefied field region. These field E+A galaxies can not be explained by the cluster related phenomena. The optical-infrared colors of E+A galaxies are not much redder than normal galaxies. Radio derived star formation rate shows that E+As are not dusty starbursting galaxies. Therefore, dusty star formation origin is not plausible. Based on the population synthesis model, we identified young E+A galaxies as a galaxy 270-430 Myrs after the burst (E+As with Hδ EW > 7Å). While examining the image of these galaxies, we found that the young E+As often have accompanying galaxies. Statistically, these galaxies have, in fact, accompanying galaxies ˜2.5 (8.0) times more frequent than randomly selected galaxies within 75 (50) kpc at two σ significance level. Considering that neither the dusty origin nor the cluster origin is plausible, we conclude that merger/interaction with closely accompanying galaxies is the most likely mechanism to be responsible for the E+A phenomenon.
Goto Tomotsugu
SDSS Collaboration
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