CONSTRAINTS ON THE FAINT END OF THE QUASAR LUMINOSITY FUNCTION AT z {approx} 5 IN THE COSMOS FIELD

Journal Article · Mon Sep 10 04:00:00 EDT 2012 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/756/2/160· OSTI ID:22092348

Ikeda, H.; Matsuoka, K.; Kajisawa, M. ^[1]; Nagao, T. ^[2]; Taniguchi, Y.; Shioya, Y. ^[3]; Enoki, M. ^[4]; Capak, P.; Masters, D.; Scoville, N. Z. ^[5]; Civano, F. ^[6]; Koekemoer, A. M. ^[7]; Morokuma, T. ^[8]; Salvato, M. ^[9]

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1. Graduate School of Science and Engineering, Ehime University, Bunkyo-cho, Matsuyama 790-8577 (Japan)
2. Department of Astronomy, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502 (Japan)
3. Research Center for Space and Cosmic Evolution, Ehime University, Bunkyo-cho, Matsuyama 790-8577 (Japan)
4. Faculty of Business Administration, Tokyo Keizai University, 1-7-34 Minami-cho, Kokubunji, Tokyo 185-8502 (Japan)
5. Department of Astronomy, 249-17 Caltech, 1201 East California Boulevard, Pasadena, CA 91125 (United States)
6. Harvard Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
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. Max-Planck-Institut fuer Plasmaphysik, Boltzmanstrasse 2, D-85741 Garching (Germany)

We present the result of our low-luminosity quasar survey in the redshift range of 4.5 {approx}< z {approx}< 5.5 in the COSMOS field. Using the COSMOS photometric catalog, we selected 15 quasar candidates with 22 < i' < 24 at z {approx} 5 that are {approx}3 mag fainter than the Sloan Digital Sky Survey quasars in the same redshift range. We obtained optical spectra for 14 of the 15 candidates using FOCAS on the Subaru Telescope and did not identify any low-luminosity type-1 quasars at z {approx} 5, while a low-luminosity type-2 quasar at z {approx} 5.07 was discovered. In order to constrain the faint end of the quasar luminosity function at z {approx} 5, we calculated the 1{sigma} confidence upper limits of the space density of type-1 quasars. As a result, the 1{sigma} confidence upper limits on the quasar space density are {Phi} < 1.33 Multiplication-Sign 10{sup -7} Mpc{sup -3} mag{sup -1} for -24.52 < M{sub 1450} < -23.52 and {Phi} < 2.88 Multiplication-Sign 10{sup -7} Mpc{sup -3} mag{sup -1} for -23.52 < M{sub 1450} < -22.52. The inferred 1{sigma} confidence upper limits of the space density are then used to provide constraints on the faint-end slope and the break absolute magnitude of the quasar luminosity function at z {approx} 5. We find that the quasar space density decreases gradually as a function of redshift at low luminosity (M{sub 1450} {approx} -23), being similar to the trend found for quasars with high luminosity (M{sub 1450} < -26). This result is consistent with the so-called downsizing evolution of quasars seen at lower redshifts.

• OSTI ID: 22092348
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 756; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ASTRONOMY
ASTROPHYSICS
CATALOGS
COSMOLOGY
DENSITY
LUMINOSITY
QUASARS
RED SHIFT
STAR EVOLUTION
TELESCOPES
UNIVERSE
VISIBLE SPECTRA