CaltechAUTHORS
Published February 20, 2011 | Version Published
Journal Article Open

Probing the Faint End of the Quasar Luminosity Function at z~4 in the COSMOS Field

Creators

  • 1. ROR icon Ehime University
  • 2. ROR icon Japan Society for the Promotion of Science
  • 3. ROR icon University of California, Santa Cruz
  • 4. ROR icon California Institute of Technology
  • 5. ROR icon Tokyo Keizai University
  • 6. ROR icon Space Telescope Science Institute
  • 7. ROR icon University of Tokyo
  • 8. ROR icon Tohoku University
  • 9. ROR icon Kavli Institute for the Physics and Mathematics of the Universe
  • 10. ROR icon Max Planck Institute for Plasma Physics
  • 11. ROR icon Max Planck Institute for Astronomy

Abstract

We searched for quasars that are ~3 mag fainter than the SDSS quasars in the redshift range 3.7 ≾ z ≾ 4.7 in the COSMOS field to constrain the faint end of the quasar luminosity function (QLF). Using optical photometric data, we selected 31 quasar candidates with 22 < i < 24 at z ~ 4. We obtained optical spectra for most of these candidates using FOCAS on the Subaru telescope and identified eight low-luminosity quasars at z ~ 4. In order to derive the QLF based on our spectroscopic follow-up campaign, we estimated the photometric completeness of our quasar survey through detailed Monte Carlo simulations. Our QLF at z ~ 4 has a much shallower faint-end slope (β = −1.67^(+0.11)_(−0.17)) than that obtained by other recent surveys in the same redshift. Our result is consistent with the scenario of downsizing evolution of active galactic nuclei inferred by recent optical and X-ray quasar surveys at lower redshifts.

Additional Information

© 2011 American Astronomical Society. Received 2010 November 9; accepted 2010 December 20; published 2011 January 25. We thank the Subaru staff for their invaluable help and all members of the COSMOS team. T.M., K.M., and Y.I. are financially supported by the Japan Society for the Promotion of Science (JSPS) through the JSPS Research Fellowship.

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Published - Ikeda2011p13025Astrophys_J_Lett.pdf

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Additional details

Identifiers

Eprint ID
22962
Resolver ID
CaltechAUTHORS:20110317-130412253

Funding

Japan Society for the Promotion of Science (JSPS)

Dates

Created
2011-03-18
Created from EPrint's datestamp field
Updated
2021-11-09
Created from EPrint's last_modified field

Caltech Custom Metadata

Caltech groups
COSMOS , Infrared Processing and Analysis Center (IPAC)