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

Abstract

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 deg2 of the Sloan Digital Sky Survey Stripe 82 region. Most of these sources are in the QSO luminosity regime (L bol ≳ 1012 L ⊙) 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 as [O iii] line luminosity (L [O iii]) and 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 > 1045 erg s−1, while the fraction of Type-2 AGNs with L 5μm < 1045 erg s−1 rises sharply from 40% to 80% of the overall AGN population.