{
  "id": "astro-ph/9901237",
  "version": "v1",
  "published": "1999-01-18T21:25:00.000Z",
  "updated": "1999-01-18T21:25:00.000Z",
  "title": "Faint galaxies, extragalactic background light, and the reionization of the Universe",
  "authors": [
    "Piero Madau"
  ],
  "comment": "LateX, 13 pages, aipproc.sty, 5 figures. To appear in the proceedings of the 9th Annual October Astrophysics Conference in Maryland, ``After the Dark Ages: When Galaxies were Young\", edited by S. S. Holt and E. P. Smith",
  "doi": "10.1063/1.58615",
  "categories": [
    "astro-ph"
  ],
  "abstract": "I review recent observational and theoretical progress in our understanding of the cosmic evolution of luminous sources. Largely due to a combination of deep HST imaging, Keck spectroscopy, and COBE far-IR background measurements, new constraints have emerged on the emission history of the galaxy population as a whole. Barring large systematic effects, the global ultraviolet, optical, near- and far-IR photometric properties of galaxies as a function of cosmic time cannot be reproduced by a simple stellar evolution model defined by a constant (comoving) star-formation density and a universal (Salpeter) IMF, and require instead a substantial increase in the stellar birthrate with lookback time. While the bulk of the stars present today appears to have formed relatively recently, the existence of a decline in the star-formation density above z=2 remains uncertain. The history of the transition from the cosmic `dark age' to a ionized universe populated with luminous sources can constrain the star formation activity at high redshifts. If stellar sources are responsible for photoionizing the intergalactic medium at z=5, the rate of star formation at this epoch must be comparable or greater than the one inferred from optical observations of galaxies at z=3. A population of dusty, Type II AGNs at z<2 could make a significant contribution to the FIR background if the accretion efficiency is of order 10%.",
  "revisions": [
    {
      "version": "v1",
      "updated": "1999-01-18T21:25:00.000Z"
    }
  ],
  "analyses": {
    "subjects": [
      "98.80.-k",
      "98.62.Ai",
      "98.70.Vc",
      "95.30.Gv"
    ],
    "keywords": [
      "extragalactic background light",
      "faint galaxies",
      "stellar evolution model",
      "star formation",
      "star-formation density"
    ],
    "tags": [
      "conference paper",
      "journal article"
    ],
    "note": {
      "typesetting": "LaTeX",
      "pages": 13,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "inspire": 494146,
      "adsabs": "1999AIPC..470..299M"
    }
  }
}