{
  "id": "astro-ph/0509894",
  "version": "v1",
  "published": "2005-09-30T01:29:46.000Z",
  "updated": "2005-09-30T01:29:46.000Z",
  "title": "Star Formation Rates and Extinction Properties of IR-Luminous Galaxies in the Spitzer First Look Survey",
  "authors": [
    "P. I. Choi",
    "L. Yan",
    "M. Im",
    "G. Helou",
    "B. T. Soifer",
    "L. J. Storrie-Lombardi",
    "R. Chary",
    "H. I. Teplitz",
    "D. Fadda",
    "F. R. Marleau",
    "M. Lacy",
    "G. Wilson",
    "P. N. Appleton",
    "D. T. Frayer",
    "J. A. Surace"
  ],
  "comment": "accepted by the Astrophysical Journal; 19 pages, including 14 figures",
  "journal": "Astrophys.J.637:227-241,2006",
  "doi": "10.1086/498388",
  "categories": [
    "astro-ph"
  ],
  "abstract": "We investigate the instantaneous star formation rates (SFR) and extinction properties for a large (N=274), near-infrared (2.2 micron) + mid-infrared (24 micron) selected sample of normal to ultra-luminous infrared galaxies (ULIRGs) [10^9<L_{IR}/L_{sun}<10^12.5] with <z>~0.8 in the Spitzer Extragalactic First Look Survey. We combine Spitzer MIPS 24-micron observations with high-resolution, optical Keck Deimos spectroscopy to derive optical emission-line and infrared star formation rates (SFR_{opt} & SFR_{IR}, respectively). Direct comparison of these SFR diagnostics reveals that our sample exhibits a wide range of extinction (1.0<Av<4.0 mag). This is after removing spectroscopic and IRAC color-selected AGN candidates that account for 12% of the sample. Objects with SFRs of a few solar masses per year have Av values consistent with those of normal spirals (Av~1.0 mag). By contrast, LIRGs at z>1, which make up a large fraction of our sample, have SFR~100 M_{sun}/yr and <Av>~2.5 mag. This translates to a 97% mean attenuation of the [OII] forbidden line doublet, with the most extreme sources having as much as 99.7% of their [OII] line flux extinguished by dust. Based on a SFR_{IR}/SFR_{opt} diagnostic, we derive an IR-luminosity-dependent Av^{IR} function [Av^{IR}=0.75*log(L_{IR}/L_{sun})-6.35 mag] that we use to extinction correct our emission line luminosities. Application of this correction results in a correlation between SFR_{IR} and SFR_{opt} that has a dispersion of 0.2 dex. Investigation of the Av dependence on redshift reveals that for a fixed L_{IR}, there is no significant Av evolution. The mean attenuation of our sample is intermediate between that of local optical/UV- and radio-selected samples and has a marginally stronger L_{IR} dependence.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2005-09-30T01:29:46.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "star formation rates",
      "spitzer first look survey",
      "extinction properties",
      "ir-luminous galaxies",
      "spitzer extragalactic first look survey"
    ],
    "tags": [
      "journal article"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 19,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 693706
    }
  }
}