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Quasars with highly accreting black holes: their X-ray properties and modified prescription of single-epoch mass

Presentation #316.02D in the session AGN and Quasars V.

Published onJun 29, 2022
Quasars with highly accreting black holes: their X-ray properties and modified prescription of single-epoch mass

The mass and accretion rate is essential to quantify the growth of the black holes, their evolution, and their impact on the host galaxies. Recent reverberation-mapped active galactic nuclei (AGNs) show that the highest accretion rate objects have a systematic smaller broad-line region (BLR) radius, 3-8 times smaller than predicted by traditional radius-luminosity (R–L) relationships. I examined the X-ray and optical-UV (OUV) properties of a dozen super-Eddington accreting black holes (SEAMBHs) that show extreme deviation from the canonical R-L relationship. Their X-ray properties may be diagnostic of structural changes in their accretion disks that may explain such behavior. I will present new Chandra X-ray and follow-up OUV observations of these SEAMBHs. They indeed have a steep hard X-ray photon index, Γ, and demonstrate a steeper power-law slope, αox, and these properties correlate with accretion rate. As highly accreting AGNs have a smaller BLR radius than previously realized, they need modified prescriptions for single-epoch virial black hole mass estimates. A new R-L relationship by Du & Wang (2019) corrects for accretion rate biases by incorporating the flux ratio of optical Fe II to Hβ. I will present the result of using this R-L relationship to estimate the black hole mass and accretion rate parameters of quasars in a wide range of redshifts. Failure to use a Fe-corrected R-L relationship results in the virial mass overestimated by a factor of two, on average, and up to an order of magnitude for highly accreting black holes.

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