A Composite Broad-Line Region in SDSS J1609+4902: a Double-Peaked Disk component and a Gaussian Component

2025/06/08 by Wu, Jiancheng, Wu, Qingwen, Hu, Chen +6
#Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences #High Energy Astrophysical Phenomena (astro-ph.HE)

paper · doi:10.48550/arxiv.2506.07161

Abstract

The profiles of broad emission lines in active galactic nuclei (AGNs) provide critical insights into the geometry and kinematics of the broad-line region (BLR), which in turn influence the uncertainties in estimating the masses of central supermassive black holes. In this study, we report the discovery of a low-luminosity AGN, SDSS J1609+4902, in which the Hα line exhibits two distinct BLR components: a Gaussian component and an extremely broad double-peaked component. Follow-up observations conducted at the Lijiang Observatory in 2025 reveal that the line profile remains roughly unchanged, suggesting that this BLR structure may remain stable over a timescale of ∼10 years. We find that the size of the central Gaussian (Full Width at Half Maximum, FWHM∼ 3000 \rm km s^-1) component is consistent with the classical reverberation mapping correlation. In contrast, the asymmetric double-peaked wing (FWHM∼ 23,000 \rm km s^-1) likely originates from a disk-like BLR with an inner radius of approximately 70 gravitational radii. These results provide new constraints on the structure and dynamics of BLRs in AGNs and highlight the potential for long-term stability in such systems.

Citations

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Related

• The SDSS-V Black Hole Mapper Reverberation Mapping Project: Multi-Line Dynamical Modeling of a Highly Variable Active Galactic Nucleus with Decade-long Light Curves
• Exploring variation of double-peak broad-line profile in strongly variable AGNs
• Broad-line region geometry from multiple emission lines in a single-epoch spectrum
• A candidate for central tidal disruption event in the broad line AGN SDSS J1605 with double-peaked broad Hβ
• Probing the origin of the two-component structure of broad line region by reverberation mapping of an extremely variable quasar