Estimating Black Hole Masses in Obscured AGN from X-ray and Optical Emission Line Luminosities
Fuente:
arXiv
Saved in:
| Main Authors: | , , , , , , , , |
|---|---|
| Format: | Preprint |
| Published: |
2025
|
| Subjects: | |
| Online Access: | |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| _version_ | 1866917901466861568 |
|---|---|
| author | LaMassa, S. Farrow, I. Urry, C. M. Trakhtenbrot, B. Auge, C. Koss, M. J. Peca, A. Sanders, D. Turner, T. J. |
| author_facet | LaMassa, S. Farrow, I. Urry, C. M. Trakhtenbrot, B. Auge, C. Koss, M. J. Peca, A. Sanders, D. Turner, T. J. |
| contents | 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 H$α$ (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 $0.32 \pm 0.68$ dex between these methods, which propagates to a factor of $\sim$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 Pa$α$ (Pa$β$) 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 $\pm$ 0.44 dex (0.48 $\pm$ 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 $\sim$3-5. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2501_14072 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Estimating Black Hole Masses in Obscured AGN from X-ray and Optical Emission Line Luminosities LaMassa, S. Farrow, I. Urry, C. M. Trakhtenbrot, B. Auge, C. Koss, M. J. Peca, A. Sanders, D. Turner, T. J. Astrophysics of Galaxies High Energy Astrophysical Phenomena We test a novel method for estimating black hole masses ($M_{\rm BH}$) in obscured active galactic nuclei (AGN) that uses proxies to measure the full-width half maximum of broad H$α$ (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 $0.32 \pm 0.68$ dex between these methods, which propagates to a factor of $\sim$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 Pa$α$ (Pa$β$) 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 $\pm$ 0.44 dex (0.48 $\pm$ 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 $\sim$3-5. |
| title | Estimating Black Hole Masses in Obscured AGN from X-ray and Optical Emission Line Luminosities |
| topic | Astrophysics of Galaxies High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2501.14072 |