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Title: A glimpse at quasar host galaxy far-UV emission using damped Lyα's as natural coronagraphs

In merger-driven models of massive galaxy evolution, the luminous quasar phase is expected to be accompanied by vigorous star formation in quasar host galaxies. In this paper, we use high column density damped Lyα (DLA) systems along quasar sight lines as natural coronagraphs to directly study the far-UV (FUV) radiation from the host galaxies of luminous background quasars. We have stacked the spectra of ∼2000 DLA systems (N {sub H} {sub I} > 10{sup 20.6} cm{sup –2}) with a median absorption redshift (z) = 2.6 selected from quasars observed in the SDSS-III Baryon Oscillation Spectroscopic Survey. We detect residual flux in the dark troughs of the composite DLA spectra. The level of this residual flux significantly exceeds systematic errors in the Sloan Digital Sky Survey fiber sky subtraction; furthermore, the residual flux is strongly correlated with the continuum luminosity of the background quasar, while uncorrelated with DLA column density or metallicity. We conclude that the flux could be associated with the average FUV radiation from the background quasar host galaxies (with medium redshift (z) = 3.1) that is not blocked by the intervening DLA. Assuming that all of the detected flux originates from quasar hosts, for the highest quasar luminositymore » bin ((L) = 2.5 × 10{sup 13} L {sub ☉}), the host galaxy has an FUV intensity of 1.5 ± 0.2 × 10{sup 40} erg s{sup –1} Å{sup –1}; this corresponds to an unobscured UV star formation rate of 9 M {sub ☉} yr{sup –1}.« less
Authors:
; ; ;  [1] ; ; ;  [2] ;  [3] ;  [4] ;  [5] ;  [6] ;  [7] ;  [8] ;  [9] ;  [10]
  1. Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States)
  2. Institut d'Astrophysique de Paris, CNRS-UPMC, UMR7095, 98bis bd Arago, F-75014 Paris (France)
  3. Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA (United States)
  4. Research School of Astronomy and Astrophysics, Australian National University, Canberra, Weston Creek, ACT, 2611 (Australia)
  5. Institució Catalana de Recerca i Estudis Avançats, Barcelona (Spain)
  6. Departamento de Astronomia, Universidad de Chile, Casilla 36-D, Santiago (Chile)
  7. Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States)
  8. Department of Physics and Astronomy, Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218 (United States)
  9. Department of Astronomy, University of Florida, Gainesville, FL (United States)
  10. Brookhaven National Laboratory, Upton, NY 11973 (United States)
Publication Date:
OSTI Identifier:
22370539
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 793; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABSORPTION; COSMOLOGY; DENSITY; EMISSION; GALAXIES; LUMINOSITY; LYMAN LINES; METALLICITY; OSCILLATIONS; QUASARS; RED SHIFT; SPECTRA; STARS; STELLAR CORONAE