2005ApJ...633..630W -
Astrophys. J., 633, 630-637 (2005/November-2)
First results from the Canada-France high-z quasar survey: constraints on the z=6 quasar luminosity function and the quasar contribution to reionization.
WILLOTT C.J., DELFOSSE X., FORVEILLE T., DELORME P. and GWYN S.D.J.
Abstract (from CDS):
We present preliminary results of a new quasar survey being undertaken with multicolor optical imaging from the Canada-France-Hawaii Telescope. The current data consist of 3.83 deg2 of imaging in the i' and z' filters to a 10 σ limit of z'<23.35. Near-infrared photometry of 24 candidate 5.7<z<6.4 quasars confirms them all to be low-mass stars, including two T dwarfs and four or five L dwarfs. Photometric estimates of the spectral type of the two T dwarfs are T3 and T6. We use the lack of high-redshift quasars in this survey volume to constrain the z=6 quasar luminosity function. For reasonable values of the break absolute magnitude M*1450and faint-end slope α, we determine that the bright-end slope β>-3.2 at 95% confidence. We find that the comoving space density of quasars brighter than M1450=-23.5 declines by a factor of >25 from z=2 to 6, mirroring the decline observed for high-luminosity quasars. We consider the contribution of the quasar population to the ionizing photon density at z=6 and the implications for reionization. We show that the current constraints on the quasar population give an ionizing photon density ≪30% that of the star-forming galaxy population. We conclude that active galactic nuclei make a negligible contribution to the reionization of hydrogen at z∼6.
Abstract Copyright:
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Journal keyword(s):
Cosmology: Observations - Galaxies: Active - Galaxies: Quasars: General
VizieR on-line data:
<Available at CDS (J/ApJ/633/630): table1.dat>
Nomenclature:
Table 1: [WDF2005] CFHTLS JHHMMSS.ss+DDMMSS.s N=24.
Simbad objects:
25
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