BASS LII: The prevalence of double-peaked broad lines at low accretion rates among hard X-ray selected AGN
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| Format: | Preprint |
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2025
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| author | Ward, Charlotte Koss, Michael J. Eracleous, Michael Trakhtenbrot, Benny Bauer, Franz E. Caglar, Turgay Harrison, Fiona Jana, Arghajit Kakkad, Darshan Magno, Macon del Moral-Castro, Ignacio Mushotzky, Richard Oh, Kyuseok Peca, Alessandro Powell, Meredith C. Ricci, Claudio Rojas, Alejandra Smith, Krista Lynne Stern, Daniel Treister, Ezequiel Urry, C. Megan |
| author_facet | Ward, Charlotte Koss, Michael J. Eracleous, Michael Trakhtenbrot, Benny Bauer, Franz E. Caglar, Turgay Harrison, Fiona Jana, Arghajit Kakkad, Darshan Magno, Macon del Moral-Castro, Ignacio Mushotzky, Richard Oh, Kyuseok Peca, Alessandro Powell, Meredith C. Ricci, Claudio Rojas, Alejandra Smith, Krista Lynne Stern, Daniel Treister, Ezequiel Urry, C. Megan |
| contents | A fraction of active galactic nuclei (AGN) have double-peaked H$α$, H$β$ and Mg II broad lines attributed to emission from rotating gas in the accretion disk. Using optical spectroscopy of a flux-limited sample of AGN selected via ultrahard X-rays from the BAT AGN Spectroscopic Survey (BASS), we systematically identify 71 double-peaked emitters amongst 343 broad-line AGN with redshifts $0.004<z<0.297$ and 2-10 KeV X-ray luminosities of log 40-45.7 (erg/s), and provide their best-fit accretion disk geometry parameters. We find that ~21% of X-ray selected broad-line AGN are double-peaked emitters (DPEs), consistent with rates previously reported for $z<0.2$ broad-line AGN selected for strong optical variability in ZTF. 11 of 71 DPEs (15%) exhibited a single-peaked Gaussian component to the broad line profile in addition to the double-peaked disk profile. In this sample, DPEs have intrinsically higher masses by ~0.4 dex and lower Eddington ratios by ~0.3 dex than other broad-line AGN, and have a preference for elliptical host galaxies, higher X-ray luminosities, and higher [OI] $λ$6302 to narrow H$α$ flux ratios than other broad-line AGN. We find that DPEs are not segregated from other broad-line AGN in the $L_{\rm bol}$ vs $M_{\rm BH}$ relation or their X-ray to radio luminosity ratios, and do not show a preference for intermediate Seyfert types over Seyfert 1s. We do not find differences in a wide range of multi-wavelength properties when comparing DPEs to other broad-line AGN, including optical and mid-IR variability levels, and the rate of changing-look events. We discuss the two populations in the context of multi-component disk-wind models of the AGN broad line region and consider how unrecognized contributions of disk emission to the broad lines introduce biases in virial SMBH mass estimates. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2507_05380 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | BASS LII: The prevalence of double-peaked broad lines at low accretion rates among hard X-ray selected AGN Ward, Charlotte Koss, Michael J. Eracleous, Michael Trakhtenbrot, Benny Bauer, Franz E. Caglar, Turgay Harrison, Fiona Jana, Arghajit Kakkad, Darshan Magno, Macon del Moral-Castro, Ignacio Mushotzky, Richard Oh, Kyuseok Peca, Alessandro Powell, Meredith C. Ricci, Claudio Rojas, Alejandra Smith, Krista Lynne Stern, Daniel Treister, Ezequiel Urry, C. Megan Astrophysics of Galaxies High Energy Astrophysical Phenomena A fraction of active galactic nuclei (AGN) have double-peaked H$α$, H$β$ and Mg II broad lines attributed to emission from rotating gas in the accretion disk. Using optical spectroscopy of a flux-limited sample of AGN selected via ultrahard X-rays from the BAT AGN Spectroscopic Survey (BASS), we systematically identify 71 double-peaked emitters amongst 343 broad-line AGN with redshifts $0.004<z<0.297$ and 2-10 KeV X-ray luminosities of log 40-45.7 (erg/s), and provide their best-fit accretion disk geometry parameters. We find that ~21% of X-ray selected broad-line AGN are double-peaked emitters (DPEs), consistent with rates previously reported for $z<0.2$ broad-line AGN selected for strong optical variability in ZTF. 11 of 71 DPEs (15%) exhibited a single-peaked Gaussian component to the broad line profile in addition to the double-peaked disk profile. In this sample, DPEs have intrinsically higher masses by ~0.4 dex and lower Eddington ratios by ~0.3 dex than other broad-line AGN, and have a preference for elliptical host galaxies, higher X-ray luminosities, and higher [OI] $λ$6302 to narrow H$α$ flux ratios than other broad-line AGN. We find that DPEs are not segregated from other broad-line AGN in the $L_{\rm bol}$ vs $M_{\rm BH}$ relation or their X-ray to radio luminosity ratios, and do not show a preference for intermediate Seyfert types over Seyfert 1s. We do not find differences in a wide range of multi-wavelength properties when comparing DPEs to other broad-line AGN, including optical and mid-IR variability levels, and the rate of changing-look events. We discuss the two populations in the context of multi-component disk-wind models of the AGN broad line region and consider how unrecognized contributions of disk emission to the broad lines introduce biases in virial SMBH mass estimates. |
| title | BASS LII: The prevalence of double-peaked broad lines at low accretion rates among hard X-ray selected AGN |
| topic | Astrophysics of Galaxies High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2507.05380 |