{
  "id": "astro-ph/0612736",
  "version": "v1",
  "published": "2006-12-26T23:57:24.000Z",
  "updated": "2006-12-26T23:57:24.000Z",
  "title": "Insights into Galaxy Evolution from Mid-infrared Wavelengths",
  "authors": [
    "Ranga-Ram Chary"
  ],
  "comment": "11 pages, 6 figures, proceedings of \"At the Edge of the Universe\" conference, Sintra, Portugal, Oct 2006",
  "categories": [
    "astro-ph"
  ],
  "abstract": "In this paper, I have attempted to highlight key results from deep extragalactic surveys at mid-infrared wavelengths. I discuss advances in our understanding of dust enshrouded star-formation and AGN activity at 0<z<3 from IRAS, ISO and Spitzer. The data seem to indicate that about 70% of the co-moving star-formation rate density at 0.5<z<3 is obscured by dust and that AGN, including obscured sources, account for <20% of the co-moving bolometric luminosity density. There is tentative evidence that the mode of star-formation changes as a function of redshift; star-formation at z~2 is preferentially in massive, ultraluminous infrared galaxies (ULIRGs) while z~1 sources are luminous infrared galaxies (LIRGs) which are about 1 mag fainter than ULIRGs in the near-infrared. This evolution of the star-formation mode, is similar to the evolution of the redshift distribution of X-ray sources as a function of X-ray luminosity and would suggest an extension of the downsizing hypothesis to include both AGN and star-forming galaxies. Measuring dust-enshrouded star-formation at z>3 will become possible only with future facilities like ALMA. Currently, the presence of dust can only be assessed in a small fraction of the youngest starbursts at z>5 by looking for redshifted large equivalent width H_alpha emission in broadband filters like the IRAC 4.5 micron passband. H_alpha to UV ratios in these objects are a tracer of dust extinction and measuring this ratio in GOODS galaxies indicate dust in ~20% of star-forming galaxies at z>5. Finally, implications for reionization based on the measured stellar mass density and star-formation rates of galaxies at these redshifts are discussed.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2006-12-26T23:57:24.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "mid-infrared wavelengths",
      "galaxy evolution",
      "deep extragalactic surveys",
      "measured stellar mass density",
      "redshifted large equivalent width"
    ],
    "tags": [
      "conference paper"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 11,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 735581
    }
  }
}