Holes in the BH$^\star$? AGN signatures in the FUV spectrum of a black-hole dominated Little Red Dot at $z=7.04$
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2026
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| author | Ji, Xihan Pezzulli, Gabriele D'Eugenio, Francesco Maiolino, Roberto Carniani, Stefano Tacchella, Sandro Jones, Gareth Smith, Aaron Witstok, Joris Fabian, Andrew C. Geris, Sophia Harshan, Anishya Isobe, Yuki Ivey, Lucy R. Juodžbalis, Ignas Pascalau, Robert Scholtz, Jan Witten, Callum |
| author_facet | Ji, Xihan Pezzulli, Gabriele D'Eugenio, Francesco Maiolino, Roberto Carniani, Stefano Tacchella, Sandro Jones, Gareth Smith, Aaron Witstok, Joris Fabian, Andrew C. Geris, Sophia Harshan, Anishya Isobe, Yuki Ivey, Lucy R. Juodžbalis, Ignas Pascalau, Robert Scholtz, Jan Witten, Callum |
| contents | It has been suggested that "Little Red Dots" (LRDs) might be accreting black holes enshrouded by dense gas in a nearly closed geometry, which completely covers the central black hole, leading to an atmosphere-like structure known as the "black-hole star" ($\rm BH^\star$). We test this scenario by analysing new JWST spectroscopy in the far ultraviolet (FUV, rest-frame) of the prototypical LRD Abell2744-QSO1, at $z=7.04$. We found the presence of broad Ly$α$ emission with an FWHM of $\sim 1000$ km/s, and detections of OI, CIV, and/or FeII emission lines. The NIRCam imaging and NIRSpec slit images indicate that the low-velocity component ($v\lesssim 200$ km/s) of Ly$α$ is likely spatially extended, but the high-velocity component ($v\gtrsim 200$ km/s) of Ly$α$ remains unresolved. Based on the multi-component kinematics and flux of Ly$α$ relative to Balmer lines, we conclude that the observed line profile is unlikely to be broadened by subsequent resonant scattering through the interstellar medium. This suggests that the high-velocity component of Ly$α$ originates in the broad-line region, although resonant scattering in the dense gas likely makes Ly$α$ broader than H$α$ as observed. The nebular features of this LRD indicate that there is at least one relatively optically thin direction where Ly$α$ can escape from the broad-line region (BLR). We also found indications that photons from the BLR are powering fluorescence of FeII and OI on a larger physical scale. The FUV features thus challenge the fully-covered geometry interpretation and suggest that there are "holes" in the $\rm BH^\star$, or the absorbing medium is simply clumpy. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2604_03370 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Holes in the BH$^\star$? AGN signatures in the FUV spectrum of a black-hole dominated Little Red Dot at $z=7.04$ Ji, Xihan Pezzulli, Gabriele D'Eugenio, Francesco Maiolino, Roberto Carniani, Stefano Tacchella, Sandro Jones, Gareth Smith, Aaron Witstok, Joris Fabian, Andrew C. Geris, Sophia Harshan, Anishya Isobe, Yuki Ivey, Lucy R. Juodžbalis, Ignas Pascalau, Robert Scholtz, Jan Witten, Callum Astrophysics of Galaxies It has been suggested that "Little Red Dots" (LRDs) might be accreting black holes enshrouded by dense gas in a nearly closed geometry, which completely covers the central black hole, leading to an atmosphere-like structure known as the "black-hole star" ($\rm BH^\star$). We test this scenario by analysing new JWST spectroscopy in the far ultraviolet (FUV, rest-frame) of the prototypical LRD Abell2744-QSO1, at $z=7.04$. We found the presence of broad Ly$α$ emission with an FWHM of $\sim 1000$ km/s, and detections of OI, CIV, and/or FeII emission lines. The NIRCam imaging and NIRSpec slit images indicate that the low-velocity component ($v\lesssim 200$ km/s) of Ly$α$ is likely spatially extended, but the high-velocity component ($v\gtrsim 200$ km/s) of Ly$α$ remains unresolved. Based on the multi-component kinematics and flux of Ly$α$ relative to Balmer lines, we conclude that the observed line profile is unlikely to be broadened by subsequent resonant scattering through the interstellar medium. This suggests that the high-velocity component of Ly$α$ originates in the broad-line region, although resonant scattering in the dense gas likely makes Ly$α$ broader than H$α$ as observed. The nebular features of this LRD indicate that there is at least one relatively optically thin direction where Ly$α$ can escape from the broad-line region (BLR). We also found indications that photons from the BLR are powering fluorescence of FeII and OI on a larger physical scale. The FUV features thus challenge the fully-covered geometry interpretation and suggest that there are "holes" in the $\rm BH^\star$, or the absorbing medium is simply clumpy. |
| title | Holes in the BH$^\star$? AGN signatures in the FUV spectrum of a black-hole dominated Little Red Dot at $z=7.04$ |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2604.03370 |