NOAO >   Observing Info >   Approved Programs >   2006A-0194

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Proposal Information for 2006A-0194


PI: Chisato Yamauch, Japan Aerospace Exploration Agency, cyamauch@optik.mtk.nao.ac.jp
Address: Institute of Space and Astronautical Science, 3-1-1 Yoshinodai, Sagamihara, Kanagawa 229-8510, Japan

CoI: Tomotsugu Goto, Japan Aerospace Exploration Agency
CoI: Masafumi Yagi, National Astronomical Observatory, Japan

Title: Physically associated companion of E+A Galaxies - II

Abstract: The subject of this proposal is to identify physically associated companions of E+A galaxies, and to obtain basic spectroscopic features of bright companions in order to understand the evolution of E+A system. E+A galaxies have been understood as post-starburst galaxies based on their strong Balmer absorption lines and the absence of [OII] or H(alpha) emission lines. Their origin has remained unknown for more than 20 years since E+As are very rare. To rectify the situation, Goto (2003,2005) has selected large & uniform E+A sample using the Sloan Digital Sky Survey (SDSS) data. Goto (2003) found that there is an excess in number of accompanying galaxies of E+As in the SDSS imaging data, and suggest that the origin of E+As is dynamical merger/interaction with companion galaxies. The merger/interaction origin scenario also implies that E+As can be progenitors of early-type galaxies and play important roles in galaxy evolution. The discussion of Goto (2003) was based on the imaging data. The accompanying galaxies are not spectroscopically observed in the SDSS, and therefore it is unknown which galaxy is a real companion of E+A. We therefore propose spectroscopic observation to identify physically associated companions, and to construct a companion catalog without any contamination of fore/background overlapping galaxies. The correlation between properties of E+A and those of companions would give us great hints for understanding the evolution of the E+A system, and set constraints on the theoretical models of the E+A formation.


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