Journal Article

E+A and companion galaxies – I. A catalogue and statistics

Chisato Yamauchi, Masafumi Yagi and Tomotsugu Goto

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 390, issue 1, pages 383-398
Published in print October 2008 | ISSN: 0035-8711
Published online October 2008 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2008.13756.x
E+A and companion galaxies – I. A catalogue and statistics

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Based on our intensive spectroscopic campaign with the GoldCam spectrograph on the Kitt Peak National Observatory (KPNO) 2.1-m telescope, we have constructed the first catalogue of E+A galaxies with spectroscopic companion galaxies, and investigated a probability that an E+A galaxy has close companion galaxies. We selected 660 E+A galaxies with 4.0 Å < Hδ EW at a redshift of <0.167 from the Data Release 5 of the Sloan Digital Sky Survey (SDSS). We selected their companion candidates from the SDSS imaging data, and classified them into true companions, fore/background galaxies and companion candidates using the SDSS and our KPNO spectra. We observed 26 companion candidates of E+A galaxies at the KPNO to measure their redshifts. Their spectra showed that 17 targets are true companion galaxies. The number of spectroscopically confirmed E+A's companions is now 34. This becomes the first catalogue of E+A galaxies with spectroscopic companion systems. We found that E+A galaxies have 54 per cent larger probability of having companion galaxies (7.88 per cent) as compared to the comparison sample of normal galaxies (5.12 per cent). A statistical test shows that the probabilities are different with 99.7 per cent significance. Our results based on spectroscopy tighten the connection between the dynamical merger/interaction and the origin of E+A galaxies.

Keywords: galaxies: evolution; galaxies: interactions; galaxies: peculiar; galaxies: starburst

Journal Article.  7180 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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