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A Snapshot Survey for Gravitational Lenses Among z>=4.0 Quasars: I. The z>5.7 Sample
Journal article   Open access

A Snapshot Survey for Gravitational Lenses Among z>=4.0 Quasars: I. The z>5.7 Sample

Gordon T Richards, Michael A Strauss, Bartosz Pindor, Zoltan Haiman, Xiaohui Fan, Daniel Eisenstein, Donald P Schneider, Neta A Bahcall, J Brinkmann and Robert Brunner
The Astronomical journal, v 127(3), pp 1305-1312
09 Sep 2003
url
https://doi.org/10.1086/381906View
Published, Version of Record (VoR)Maybe Open Access (Publisher Bronze) Open

Abstract

Physics - Astrophysics of Galaxies Physics - Cosmology and Nongalactic Astrophysics Physics - Earth and Planetary Astrophysics Physics - High Energy Astrophysical Phenomena Physics - Instrumentation and Methods for Astrophysics Physics - Solar and Stellar Astrophysics
Astron.J. 127 (2004) 1305 Over the last few years, the Sloan Digital Sky Survey (SDSS) has discovered several hundred quasars with redshift between 4.0 and 6.4. Including the effects of magnification bias, one expects a priori that an appreciable fraction of these objects are gravitationally lensed. We have used the Advanced Camera for Surveys on the Hubble Space Telescope to carry out a snapshot imaging survey of high-redshift SDSS quasars to search for gravitationally split lenses. This paper, the first in a series reporting the results of the survey, describes snapshot observations of four quasars at z = 5.74, 5.82, 5.99 and 6.30, respectively. We find that none of these objects has a lensed companion within 5 magnitudes with a separation larger than 0.3 arcseconds; within 2.5 magnitudes, we can rule out companions within 0.1 arcseconds. Based on the non-detection of strong lensing in these four systems, we constrain the z~6 luminosity function to a slope of beta>-4.63 (3 sigma), assuming a break in the quasar luminosity function at M_{1450}^*=-24.0. We discuss the implications of this constraint on the ionizing background due to quasars in the early universe. Given that these quasars are not highly magnified, estimates of the masses of their central engines by the Eddington argument must be taken seriously, possibly challenging models of black hole formation.

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Astronomy & Astrophysics
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