Does the mid-infrared–hard X-ray luminosity relation for active galactic nuclei depend on Eddington ratio?. Issue 1 (2nd January 2019)

• Record Type: Journal Article
• Authors: Toba, Yoshiki; Ueda, Yoshihiro; Matsuoka, Kenta; Shidatsu, Megumi; Nagao, Tohru; Terashima, Yuichi; Wang, Wei-Hao; Chang, Yu-Yen
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 484:Issue 1(2019)
• Page Start: 196
• Page End: 203
• Publication Date: 2019-01-02
• Subjects: methods: observational -- infrared: galaxies -- X-rays: galaxies; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/sty3523
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: We revisit the correlation between the mid-infrared (6 $\rm{\mu\, m}$ ) and hard X-ray (2–10 keV) luminosities of active galactic nuclei (AGNs) to understand the physics behind it. We construct an X-ray flux-limited sample of 571 type 1 AGNs with $f_{0.5-2.0 \, {\rm keV}}\, \, \gt\, \, 2.4 \times 10^{-12}$ erg cm −2 s −1, drawn from the ROSAT Bright Survey catalogue. Cross-matching the sample with infrared data taken from Wide-field Infrared Survey Explorer, we investigate the relation between the rest-frame 6 $\rm{\mu\, m}$ luminosity ( L 6 ) and the rest-frame 2–10 keV luminosity ( L X ), where L 6 is corrected for the contamination of host galaxies using the spectral energy distribution fitting technique. We confirm that L 6 and L X are correlated over four orders of magnitude, in the range of L X = 10 42−46 erg s −1 . We investigate what kinds of physical parameters regulate this correlation. We find that L X / L 6 clearly depends on the Eddington ratio (λEdd ) as $\log \lambda _{\rm Edd} = -(0.56 \pm 0.10) \log \, (L_{\rm X}/L_{\rm 6}) - (1.07 \pm 0.05)$, even taking into account quasars that are undetected by ROSAT as well as those detected by XMM–Newton in the literature. We also add hyper-luminous quasars with L 6 > 10 46 erg s −1 in the literature and perform a correlation analysis. The resultant correlation coefficient is −0.41 ± 0.07, indicating a moderately tight correlation between L X / L 6 and λEdd . This means that AGNs with high Eddington ratios tend to have lower X-ray luminosities with respect to the mid-infrared luminosities. This dependence can be interpreted as a change in the structure of the accretion flow.