Vol 11, No 4 (2011) / Meng

IRAS F21013–0739: a possible evolutionary successor of an ultraluminous infrared galaxy

Xian-Min Meng, Hong Wu, Chen Cao

Abstract

We present a stellar population synthesis study of a type II luminous infrared galaxy, IRAS F21013-0739. Optical images show clear characteristics of a merger remnant. The H-band absolute magnitude is MH = -25.1, which is ~2 times as luminous as L galaxies. Stellar populations are obtained through the stellar synthesis code starlight. We find that it experienced a recent starburst (SB) phase ~100 Myr ago. By reconstructing the ultraviolet-to-optical spectrum, and adopting Calzetti et al. and Leitherer et al.'s extinction curves, we estimate the past infrared (IR) luminosities of the host galaxy and find it may have experienced an ultraluminous infrared galaxy phase which lasted for about 100 Myr. Its i-band absolute magnitude is Mi = -22.463, and its spectral type shows type 2 active galactic nucleus (AGN) characteristics. The mass of the supermassive black-hole is estimated to be MBH = 1.6 × 107M (lower- limit). The Eddington ratio Lbol /LEdd is 0.15, which is typical of Palomar-Green (PG) quasars. Both the nuclear SB and AGN contribute to the present IR luminosity bud get, and the SB contributes ~67%. On the diagram of IR color versus IR/optical excess, it is located between IR quasars and PG quasars. These results indicate that IRAS F21013-0739 has probably evolved from a ULIRG, and it can possibly evolve into an AGN.

 


Keywords


infrared: galaxies — galaxies: evolution — galaxies: starburst — galaxies: individual (IRAS F21013–0739) — galaxies: stellar content

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