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The X-Ray and Mid-infrared Luminosities in Luminous Type 1 Quasars

Lookup NU author(s): Dr Christopher HarrisonORCiD



This is the final published version of an article that has been published in its final definitive form by Institute of Physics Publishing, 2017.

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© 2017. The American Astronomical Society. All rights reserved.Several recent studies have reported different intrinsic correlations between the active galactic nucleus (AGN) mid-IR luminosity (LMIR) and the rest-frame 2-10 keV luminosity (LX) for luminous quasars. To understand the origin of the difference in the observed LX-LMIR relations, we study a sample of 3247 spectroscopically confirmed type 1 AGNs collected from Boötes, XMM-COSMOS, XMM-XXL-North, and the Sloan Digital Sky Survey quasars in the Swift/XRT footprint spanning over four orders of magnitude in luminosity. We carefully examine how different observational constraints impact the observed LX-LMIR relations, including the inclusion of X-ray-nondetected objects, possible X-ray absorption in type 1 AGNs, X-ray flux limits, and star formation contamination. We find that the primary factor driving the different LX-LMIR relations reported in the literature is the X-ray flux limits for different studies. When taking these effects into account, we find that the X-ray luminosity and mid-IR luminosity (measured at rest-frame 6 μm, or L6 μm) of our sample of type 1 AGNs follow a bilinear relation in the log-log plane: log LX = (0.84 ± 0.03) × log L6 μm 1045 erg s-1 + = (44.60 ± 0.01) for L6 μ <1044.79 erg s-1, and log LX = (0.40±0.03) × log L6 μm/1045 + erg s-1 +(44.51 ± 0.01) for L6 μm ≥ 1044.79 erg s-1. This suggests that the luminous type 1 quasars have a shallower LX-L6 μm correlation than the approximately linear relations found in local Seyfert galaxies. This result is consistent with previous studies reporting a luminosity-dependent LX-LMIR relation and implies that assuming a linear LX-L6 μm relation to infer the neutral gas column density for X-ray absorption might overestimate the column densities in luminous quasars.

Publication metadata

Author(s): Chen C-TJ, Hickox RC, Goulding AD, Stern D, Assef R, Kochanek CS, Brown MJI, Harrison CM, Hainline KN, Alberts S, Alexander DM, Brodwin M, Moro AD, Forman WR, Gorjian V, Jones C, Murray SS, Pope A, Rovilos E

Publication type: Article

Publication status: Published

Journal: Astrophysical Journal

Year: 2017

Volume: 837

Issue: 2

Online publication date: 13/03/2017

Acceptance date: 17/01/2017

Date deposited: 05/02/2020

ISSN (print): 0004-637X

ISSN (electronic): 1538-4357

Publisher: Institute of Physics Publishing


DOI: 10.3847/1538-4357/837/2/145


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