BlackTHUNDER strikes twice: rest-frame Balmer-line absorption and high Eddington accretion rate in a Little Red Dot at $z=7.04$
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2025
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| author | D'Eugenio, Francesco Maiolino, Roberto Perna, Michele Uebler, Hannah Ji, Xihan McClymont, William Koudmani, Sophie Sijacki, Debora Juodžbalis, Ignas Scholtz, Jan Bennett, Jake Bunker, Andrew J. Carniani, Stefano Charlot, Stéphane Cresci, Giovanni Curtis-Lake, Emma Bontà, Elena Dalla Inayoshi, Kohei Jones, Gareth C. Lyu, Jianwei Marconi, Alessandro Mazzolari, Giovanni Nelson, Erica J. Parlanti, Eleonora Robertson, Brant E. Schneider, Raffaella Simmonds, Charlotte Tacchella, Sandro Venturi, Giacomo Willott, Chris Witstok, Joris Witten, Callum |
| author_facet | D'Eugenio, Francesco Maiolino, Roberto Perna, Michele Uebler, Hannah Ji, Xihan McClymont, William Koudmani, Sophie Sijacki, Debora Juodžbalis, Ignas Scholtz, Jan Bennett, Jake Bunker, Andrew J. Carniani, Stefano Charlot, Stéphane Cresci, Giovanni Curtis-Lake, Emma Bontà, Elena Dalla Inayoshi, Kohei Jones, Gareth C. Lyu, Jianwei Marconi, Alessandro Mazzolari, Giovanni Nelson, Erica J. Parlanti, Eleonora Robertson, Brant E. Schneider, Raffaella Simmonds, Charlotte Tacchella, Sandro Venturi, Giacomo Willott, Chris Witstok, Joris Witten, Callum |
| contents | JWST has revealed a population of 'Little Red Dots' (LRDs): compact, red objects at redshifts z=2-9 with 'v'-shaped spectral energy distributions, broad permitted lines, and, often, hydrogen Balmer absorption. We use NIRSpec/IFS data from the BlackTHUNDER survey to study the H$α$ line in the LRD Abell2744-QSO1 at z=7.04, which is a confirmed AGN due to time-variable equivalent width (EW) in its broad emission lines. The H$α$ spectral profile is non-Gaussian, requiring at least two Gaussian components. We also detect a narrow-line Gaussian component, and strong H$α$ absorption (EW relative to the continuum $\sim 22_{-7}^{+12} \mathring{\mathrm{A}}$), confirming a connection between the strong Balmer break and line absorption. The absorber is at rest with respect to broad H$α$, suggesting that the gas cannot be interpreted as an inflow or outflow, forming instead a long-lived structure. Its velocity dispersion is $σ_{\rm abs}=110_{-10}^{+20}$ km s$^{-1}$, consistent with the value inferred from the analysis of the Balmer break. Based on H$α$, we infer a black hole mass of log($M_{\rm BH}/{\rm M_\odot}$)=7.2, smaller but close to the previous estimates based on H$β$. The Eddington ratio is 0.09. Combining the high signal-to-noise ratio of the narrow H$α$ line with the spectral resolution R=3,700 of the G395H grating, we infer a narrow-line intrinsic dispersion $σ_{\rm n}=22_{-6}^{+5}$ km s$^{-1}$, which places a stringent constraint on the black-hole-to-dynamical-mass ratio of this system to be $M_{\rm BH}/M_{\rm dyn}$=0.15-1.2, confirming the overmassive nature of the black hole and potentially leaving little room for a host galaxy. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2503_11752 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | BlackTHUNDER strikes twice: rest-frame Balmer-line absorption and high Eddington accretion rate in a Little Red Dot at $z=7.04$ D'Eugenio, Francesco Maiolino, Roberto Perna, Michele Uebler, Hannah Ji, Xihan McClymont, William Koudmani, Sophie Sijacki, Debora Juodžbalis, Ignas Scholtz, Jan Bennett, Jake Bunker, Andrew J. Carniani, Stefano Charlot, Stéphane Cresci, Giovanni Curtis-Lake, Emma Bontà, Elena Dalla Inayoshi, Kohei Jones, Gareth C. Lyu, Jianwei Marconi, Alessandro Mazzolari, Giovanni Nelson, Erica J. Parlanti, Eleonora Robertson, Brant E. Schneider, Raffaella Simmonds, Charlotte Tacchella, Sandro Venturi, Giacomo Willott, Chris Witstok, Joris Witten, Callum Astrophysics of Galaxies JWST has revealed a population of 'Little Red Dots' (LRDs): compact, red objects at redshifts z=2-9 with 'v'-shaped spectral energy distributions, broad permitted lines, and, often, hydrogen Balmer absorption. We use NIRSpec/IFS data from the BlackTHUNDER survey to study the H$α$ line in the LRD Abell2744-QSO1 at z=7.04, which is a confirmed AGN due to time-variable equivalent width (EW) in its broad emission lines. The H$α$ spectral profile is non-Gaussian, requiring at least two Gaussian components. We also detect a narrow-line Gaussian component, and strong H$α$ absorption (EW relative to the continuum $\sim 22_{-7}^{+12} \mathring{\mathrm{A}}$), confirming a connection between the strong Balmer break and line absorption. The absorber is at rest with respect to broad H$α$, suggesting that the gas cannot be interpreted as an inflow or outflow, forming instead a long-lived structure. Its velocity dispersion is $σ_{\rm abs}=110_{-10}^{+20}$ km s$^{-1}$, consistent with the value inferred from the analysis of the Balmer break. Based on H$α$, we infer a black hole mass of log($M_{\rm BH}/{\rm M_\odot}$)=7.2, smaller but close to the previous estimates based on H$β$. The Eddington ratio is 0.09. Combining the high signal-to-noise ratio of the narrow H$α$ line with the spectral resolution R=3,700 of the G395H grating, we infer a narrow-line intrinsic dispersion $σ_{\rm n}=22_{-6}^{+5}$ km s$^{-1}$, which places a stringent constraint on the black-hole-to-dynamical-mass ratio of this system to be $M_{\rm BH}/M_{\rm dyn}$=0.15-1.2, confirming the overmassive nature of the black hole and potentially leaving little room for a host galaxy. |
| title | BlackTHUNDER strikes twice: rest-frame Balmer-line absorption and high Eddington accretion rate in a Little Red Dot at $z=7.04$ |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2503.11752 |