2014/06/25 by Valeri Vardanyan, Daniel Weedman, Lusine Sargsyan
Engineering · Physics and Astronomy · #Active galactic nucleus #Astronomy and Astrophysical Research #Galaxies: Formation, Evolution, Phenomena #Galaxy #Infrared #Luminosity #Luminous infrared galaxy #OVV quasar #Quasar #Redshift #Sky #Space Technology and Applications #astro-ph.CO #astro-ph.GA
paper · pdf · doi:10.1088/0004-637x/790/2/88
published as ApJ 790, 88 (2014) · Accepted 2014 June 7 for publication in The Astrophysical Journal; received 2013 August 22. v2 contains reference updates added in proof
arxiv created 2014/06/25 · openalex publication_date 2014/07/08 · openalex created_date 2016/06/24 · arxiv updated 2016/08/31 · openalex updated_date 2026/08/05
Infrared luminosities ν L ν (7.8 μm) arising from dust reradiation are determined for Sloan Digital Sky Survey (SDSS) quasars with 1.4 < z < 5 using detections at 22 μm by the Wide-Field Infrared Survey Explorer . Infrared luminosity does not show a maximum at any redshift z < 5, reaching a plateau for z ≳ 3 with maximum luminosity ν L ν (7.8 μm) ≳ 10 47 erg s −1 ; luminosity functions show one quasar Gpc −3 having ν L ν (7.8 μm) > 10 46.6 erg s −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 ν L ν (0.25 μm), have the largest values of the ratio ν L ν (0.25 μm)/ν L ν (7.8 μm) 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.