Luminous WISE-selected Obscured, Unobscured, and Red Quasars in Stripe 82^∗

Abstract

We present a spectroscopically complete sample of 147 infrared-color-selected active galactic nuclei (AGNs) down to a 22 μm flux limit of 20 mJy over the ∼270 deg 2 of the Sloan Digital Sky Survey Stripe 82 region. Most of these sources are in the QSO luminosity regime (L bol  10 12 L e ) and are found out to z;3. We classify the AGNs into three types, finding 57 blue, unobscured Type-1 (broad-lined) sources; 69 obscured, Type-2 (narrow-lined) sources; and 21 moderately reddened Type-1 sources (broad-lined and E(B − V )>0.25). We study a subset of this sample in X-rays and analyze their obscuration to find that our spectroscopic classifications are in broad agreement with low, moderate, and large amounts of absorption for Type-1, red Type-1, and Type-2 AGNs, respectively. We also investigate how their X-ray luminosities correlate with other known bolometric luminosity indicators such asand infrared luminosity (L 6μm ). While the X-ray correlation with L [O III] is consistent with previous findings, the most infrared-luminous sources appear to deviate from established relations such that they are either underluminous in X-rays or overluminous in the infrared. Finally, we examine the luminosity function evolution of our sample, and by AGN type, in combination with the complementary, infrared-selected, AGN sample of Lacy et al. (2013), spanning over two orders of magnitude in luminosity. We find that the two obscured populations evolve differently, with reddened Type-1 AGNs dominating the obscured AGN fraction (∼30%) for L 5μm >10 45 erg s −1 , while the fraction of Type-2 AGNs with L 5μm <10 45 erg s −1 rises sharply from 40% to 80% of the overall AGN population.

Crossing the Line: Active Galactic Nuclei in the Star-forming Region of the BPT Diagram

“…Therefore, we next explore whether correctly and incorrectly classified X-ray AGN differ in their intrinsic AGN properties. One of the indicators of the accretion strength of an AGN in the optical regime is the luminosity of the forbidden [OIII] line, L [OIII] , which scales with the bolometric luminosity of the AGN (Mulchaey et al 1994;Heckman et al 2005;LaMassa et al 2010;Azadi et al 2017;Glikman et al 2018). A related quantity, L [OIII] divided by the fourth power of the stellar velocity dispersion, σ 4 , can provide an estimate of the Eddington ratio of the AGN (Kewley et al 2006).…”

Obscuration properties of mid-IR-selected AGN

“…In this Section, we study the X-ray absorption of the 507 IR selected AGN with X-ray detection and optical spectra. We then compare the X-ray with the optical absorption (e.g., Glikman et al 2018), using optical/mid-IR colours and SED fitting.…”

Active galactic nuclei as seen by the Spitzer Space Telescope

“…The mid-infrared luminosity function of AGNs from the combined Spitzer and Wide Field Infrared Survey Explorer (WISE) sample in ref [101]…”