PROBING THE FAINT END OF THE QUASAR LUMINOSITY FUNCTION AT z{approx} 4 IN THE COSMOS FIELD

Journal Article · Sun Feb 20 00:00:00 EST 2011 · Astrophysical Journal Letters

DOI:https://doi.org/10.1088/2041-8205/728/2/L25· OSTI ID:21560489

Ikeda, H; Nagao, T; Matsuoka, K; Ideue, Y ^[1]; Taniguchi, Y; Shioya, Y ^[2]; Trump, J R ^[3]; Capak, P; Kakazu, Y; Scoville, N Z ^[4]; Comastri, A ^[5]; Enoki, M ^[6]; Koekemoer, A M ^[7]; Morokuma, T ^[8]; Murayama, T ^[9]; Saito, T; Silverman, J D ^[10]; Salvato, M ^[11]; Schinnerer, E ^[12]

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1. Graduate School of Science and Engineering, Ehime University, Bunkyo-cho, Matsuyama 790-8577 (Japan)
2. Research Center for Space and Cosmic Evolution, Ehime University, Bunkyo-cho, Matsuyama 790-8577 (Japan)
3. UCO/Lick Observatory, Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States)
4. California Institute of Technology, MC 105-24, 1200 East California Boulevard, Pasadena, CA 91125 (United States)
5. INAF-Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna (Italy)
6. Faculty of Business Administration, Tokyo Keizai University, 1-7-34 Minami-cho, Kokubunji, Tokyo 185-8502 (Japan)
7. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
8. Institute of Astronomy, Graduate School of Science, University of Tokyo, 2-21-1 Osawa, Mitaka 181-0015 (Japan)
9. Astronomical Institute, Graduate School of Science, Tohoku University, Aramaki, Aoba, Sendai 980-8578 (Japan)
10. Institute for the Physics and Mathematics of the Universe (IPMU), University of Tokyo, Kashiwa 277-8582 (Japan)
11. Max-Planck-Institut fuer Plasmaphysik, Boltzmanstrasse 2, D-85741 Garching (Germany)
12. Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany)

We searched for quasars that are {approx}3 mag fainter than the SDSS quasars in the redshift range 3.7 {approx}< z {approx}< 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 {approx} 4. We obtained optical spectra for most of these candidates using FOCAS on the Subaru telescope and identified eight low-luminosity quasars at z {approx} 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 {approx} 4 has a much shallower faint-end slope ({beta} = -1.67{sup +0.11}{sub -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.

• OSTI ID: 21560489
• Journal Information: Astrophysical Journal Letters, Vol. 728, Issue 2; Other Information: DOI: 10.1088/2041-8205/728/2/L25; ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
COMPUTERIZED SIMULATION
EVOLUTION
GALAXY NUCLEI
LUMINOSITY
MONTE CARLO METHOD
QUASARS
RED SHIFT
SPECTRA
CALCULATION METHODS
COSMIC RADIO SOURCES
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
SIMULATION