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  • Radio Scrutiny of the X-Ray-weak Tail of Low-mass Active Galactic Nuclei: A Novel Signature of High-Eddington Accretion?
Title: Radio Scrutiny of the X-Ray-weak Tail of Low-mass Active Galactic Nuclei: A Novel Signature of High-Eddington Accretion?
The supermassive black holes (Mbh~1e6-1e10 Msun) that power luminous active galactic nuclei (AGNs), i.e., quasars, generally show a correlation between thermal disk emission in the ultraviolet (UV) and coronal emission in hard X-rays. In contrast, some “massive” black holes (mBHs; Mbh~1e5 - 1e6 Msun) in low-mass galaxies present curious X-ray properties with coronal radiative output up to 100× weaker than expected. To examine this issue, we present a pilot study incorporating Very Large Array radio observations of a sample of 18 high-accretion-rate (Eddington ratios ledd > 0.1), mBH-powered AGNs (Mbh~1e6 Msun) with Chandra X-ray coverage. Empirical correlations previously revealed in samples of radio-quiet, high-Eddington AGNs indicate that the radio–X-ray luminosity ratio, Lr/Lx, is approximately constant. Through multiwavelength analysis, we instead find that the X-ray-weaker mBHs in our sample tend toward larger values of Lr/Lx even though they remain radio-quiet per their optical–UV properties. This trend results in a tentative but highly intriguing correlation between Lr/Lx and X-ray weakness, which we argue is consistent with a scenario in which X-rays may be preferentially obscured from our line of sight by a “slim” accretion disk. We compare this observation to weak emission-line quasars (AGNs with exceptionally weak broad-line emission and a significant X-ray-weak fraction) and conclude by suggesting that our results may offer a new observational signature for finding high-accretion-rate AGNs.  more » « less
Award ID(s):
2206123
PAR ID:
10630666
Author(s) / Creator(s):
; ; ; ; ; ; ; ;
Publisher / Repository:
IOPScience
Date Published:
Journal Name:
The Astrophysical Journal
Volume:
974
Issue:
1
ISSN:
0004-637X
Page Range / eLocation ID:
66
Subject(s) / Keyword(s):
Intermediate-mass black holes Active galactic nuclei High energy astrophysics Radio quiet quasars
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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