SEEKING THE EPOCH OF MAXIMUM LUMINOSITY FOR DUSTY QUASARS

Infrared luminosities vL sub(v)(7.8 mu m) arising from dust reradiation are determined for Sloan Digital Sky Survey (SDSS) quasars with 1.4 < z < 5 using detections at 22 mu m by the Wide-Field Infrared Survey Explorer. Infrared luminosity does not show a maximum at any redshiftz z < 5, rea...

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Bibliographic Details
Published in:The Astrophysical journal 2014-08, Vol.790 (2), p.1-12
Main Authors: Vardanyan, Valeri, Weedman, Daniel, Sargsyan, Lusine
Format: Article
Language:English
Subjects:
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
COMPARATIVE EVALUATIONS
DETECTION
DISTANCE
Dust
DUSTS
EVOLUTION
Extinction
GALAXIES
Infrared
INFRARED SURVEYS
LUMINOSITY
QUASARS
RED SHIFT
Sky surveys (astronomy)
Ultraviolet
ULTRAVIOLET RADIATION
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Summary:Infrared luminosities vL sub(v)(7.8 mu m) arising from dust reradiation are determined for Sloan Digital Sky Survey (SDSS) quasars with 1.4 < z < 5 using detections at 22 mu m by the Wide-Field Infrared Survey Explorer. Infrared luminosity does not show a maximum at any redshiftz z < 5, reaching a plateau for z [gap] 3 with maximum luminosity vL sub(v)(7.8 mu m) [gap] 10 super(47) erg s super(-1); luminosity functions show one quasar Gpc super(-3) having vL sub(v)(7.8 mu m) > 10 super(46.6) erg s super(-1) for all 2 < z < 5. We conclude that the epoch when quasars first reached their maximum luminosity has not yet been identified at any redshift below 5. The most ultraviolet luminous quasars, defined by rest frame vL sub(v)(0.25 mu m), have the largest values of the ratio vL sub(v)(0.25 mu m)/vL sub(v)(7.8 mu m) with a maximum ratio at z = 2.9. From these results, we conclude that the quasars most luminous in the ultraviolet have the smallest dust content and appear luminous primarily because of lessened extinction. Observed ultraviolet/infrared luminosity ratios are used to define "obscured" quasars as those having >5 mag of ultraviolet extinction. We present a new summary of obscured quasars discovered with the Spitzer Infrared Spectrograph and determine the infrared luminosity function of these obscured quasars at z ~2.1. This is compared with infrared luminosity functions of optically discovered, unobscured quasars in the SDSS and in the AGN and Galaxy Evolution Survey. The comparison indicates comparable numbers of obscured and unobscured quasars at z ~ 2.1 with a possible excess of obscured quasars at fainter luminosities.
ISSN:0004-637X
1538-4357
DOI:10.1088/0004-637X/790/2/88