Does the mid-infrared-hard X-ray luminosity relation for active galactic nuclei depend on Eddington ratio?
Abstract
We revisit the correlation between the mid-infrared (6 {μ 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 keV} > 2.4 × 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 {μ m} luminosity (L6) and the rest-frame 2-10 keV luminosity (LX), where L6 is corrected for the contamination of host galaxies using the spectral energy distribution fitting technique. We confirm that L6 and LX are correlated over four orders of magnitude, in the range of LX = 1042-46 erg s-1. We investigate what kinds of physical parameters regulate this correlation. We find that LX/L6 clearly depends on the Eddington ratio (λEdd) as \log λ _Edd = -(0.56 ± 0.10) \log (L_X/L_6) - (1.07 ± 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 L6 > 1046 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 LX/L6 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.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- March 2019
- DOI:
- 10.1093/mnras/sty3523
- arXiv:
- arXiv:1812.09485
- Bibcode:
- 2019MNRAS.484..196T
- Keywords:
-
- methods: observational;
- infrared: galaxies;
- X-rays: galaxies;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 9 pages, 4 figures, and 2 tables, accepted for publication in MNRAS