2025/01/23 by Stephanie LaMassa, Isabella Farrow, LaMassa, S. +15
Physics and Astronomy · #Astrophysical Phenomena and Observations #Pulsars and Gravitational Waves Research #Gamma-ray bursts and supernovae
paper · pdf · doi:10.48550/arxiv.2501.14072
We test a novel method for estimating black hole masses (M\rm BH) in obscured active galactic nuclei (AGN) that uses proxies to measure the full-width half maximum of broad Hα (FWHM\rm bHα) and the accretion disk luminosity at 5100 Angstrom (λL\rm 5100 Angstrom). Using a published correlation, we estimate FWHM\rm bHα from the narrow optical emission line ratio L\rm [O III]/L\rm nHβ. Using a sample of 99 local obscured AGN from the Swift-BAT AGN Spectroscopic Survey, we assess the agreement between estimating λL\rm 5100 Angstrom from the intrinsic 2-10 keV X-ray luminosity and from narrow optical emission lines. We find a mean offset of 0.32 ± 0.68 dex between these methods, which propagates to a factor of ∼2 uncertainty when estimating M\rm BH using a virial mass formula where L\rm [O III]/L\rm nHβ serves as a proxy of FWHM\rm bHα (M\rm BH,[O III]/nHβ). We compare M\rm BH,[O III]/nHβ with virial M\rm BH measurements from broad Paschen emission lines. For the 14 (12) BASS AGN with broad Paα (Paβ) detections, we find M\rm BH,[O III]/nHβ to be systematically higher than M\rm BH,Paα (M\rm BH,Paβ) by a factor of 0.39 ± 0.44 dex (0.48 ± 0.51 dex). Since these offsets are within the scatter, more data are needed to assess whether M\rm BH,[O III]/nHβ is biased high. For 151 BASS AGN with measured stellar velocity dispersions (σ\rm *), we find that the σ\rm *-derived M\rm BH agrees with M\rm BH,[O III]/nHβ to within 0.08 dex, albeit with wide scatter (0.74 dex). The method tested here can provide estimates of M\rm BH in thousands of obscured AGN in spectroscopic surveys when other diagnostics are not available, though with an uncertainty of ∼3-5.