Probing Galaxy Evolution via Interactions and Mergers in the IRAS Revised Bright Galaxy Sample

Abstract

In order to interpret observations of luminous infrared/sub-mm galaxies and AGNs at high redshifts, and to study their evolution from the earliest epochs of star formation to the present, it is important to construct a comprehensive understanding of the properties of objects that are thought to be the closest analogs in the local Universe. These are the luminous infrared galaxies (LIRGs, L _(ir) > 10¹¹ L⊙) and ultraluminous infrared galaxies (ULIRGs, L_( ir) > 10¹² L⊙) identified in the IRAS survey. The IRAS Revised Bright Galaxy Sample (RBGS; [1]) is a complete sample of extragalactic objects with total 60 μm flux density > 5.24 Jy, covering the entire sky surveyed by IRAS at Galactic latitudes |b| > 5 degrees. The 629 objects in the RBGS have a median redshift of 0.0082, and their visual and near-infrared properties span a wide range from normal, isolated gas-rich spirals at low luminosities (L_(ir) < 10^(10.5) L⊙) through an increasing fraction of interacting galaxy pairs and ongoing mergers powered by enhanced star formation and AGNs among the LIRGs and ULIRGs. There are 22 ULIRGs (3.5%) and 180 LIRGs (29%) in the RBGS, making this an ideal sample for detailed study and comparison with observations of high-redshift galaxies. A primary goal of this study is to delineate the transformations that occur in basic properties as galaxies evolve from separate disks through the interaction and merger sequence, and possibly into elliptical galaxies.

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