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

Ikeda, H. and Nagao, T. and Matsuoka, K. and Taniguchi, Y. and Shioya, Y. and Trump, J. R. and Capak, P. and Comastri, A. and Enoki, M. and Ideue, Y. and Kakazu, Y. and Koekemoer, A. M. and Morokuma, T. and Murayama, T. and Saito, T. and Salvato, M. and Schinnerer, E. and Scoville, N. Z. and Silverman, J. D. (2011) Probing the Faint End of the Quasar Luminosity Function at z~4 in the COSMOS Field. Astrophysical Journal Letters, 728 (2). Art. No. L25. ISSN 2041-8205. doi:10.1088/2041-8205/728/2/L25.

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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.

Item Type:Article
Related URLs:
URLURL TypeDescription
Nagao, T.0000-0002-7402-5441
Matsuoka, K.0000-0002-2689-4634
Taniguchi, Y.0000-0003-2247-3741
Capak, P.0000-0003-3578-6843
Comastri, A.0000-0003-3451-9970
Koekemoer, A. M.0000-0002-6610-2048
Salvato, M.0000-0001-7116-9303
Schinnerer, E.0000-0002-3933-7677
Scoville, N. Z.0000-0002-0438-3323
Silverman, J. D.0000-0002-0000-6977
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.
Group:COSMOS, Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Japan Society for the Promotion of Science (JSPS)UNSPECIFIED
Subject Keywords:cosmology: observations; quasars: general; surveys
Issue or Number:2
Classification Code:PACS: 98.54.Aj; 95.30.Ky; 98.62.Qz; 98.62.Py
Record Number:CaltechAUTHORS:20110317-130412253
Persistent URL:
Official Citation:Probing the Faint End of the Quasar Luminosity Function at z~ 4 in the COSMOS Field H. Ikeda et al. 2011 ApJ 728 L25
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:22962
Deposited By: Ruth Sustaita
Deposited On:18 Mar 2011 14:49
Last Modified:09 Nov 2021 16:09

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