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| Autores principales: | , , , , |
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| Formato: | Preprint |
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2026
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| Acceso en línea: | https://arxiv.org/abs/2601.10573 |
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| _version_ | 1866917476159193088 |
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| author | Asada, Yoshihisa Inayoshi, Kohei Fei, Qinyue Fujimoto, Seiji Willott, Chris |
| author_facet | Asada, Yoshihisa Inayoshi, Kohei Fei, Qinyue Fujimoto, Seiji Willott, Chris |
| contents | We present a statistical study on the origins of the UV continuum and narrow/broad emission lines in little red dots (LRDs), presumably involving active galactic nuclei (AGNs). Leveraging all archived JWST/NIRSpec data, we build a sample of 27 spectroscopically-confirmed LRDs at $5<z_{\rm spec}<7.2$, by requiring broad H$α$ emission, blue UV colors, V-shaped continua, and compact morphology. We define a control sample of 7 blue, compact, broad-line AGNs without red optical continua (hereafter little blue dots; LBDs), and examine correlations between rest UV and the narrow/broad H$α$ luminosities in these populations. In LRDs, both narrow and broad H$α$ components are tightly correlated with the UV continuum, and the luminosity ratios are consistent with those in young starburst galaxies. In contrast, the UV to broad H$α$ ratios in LBDs closely match local unobscured AGNs and are statistically different from LRDs. The Ly$α$ occurrence rates and strengths do not differ between LRDs and LBDs and are comparable to normal star-forming galaxies. These results are consistent with a scenario where the central BH in LRDs is enshrouded by a dense opaque gas envelope -- in this model, the UV continuum as well as narrow and even broad H$α$ emissions are not powered by AGNs but predominantly by young massive stars surrounding the envelope, while the envelope radiates as a $\sim 5000$ K blackbody. As the envelope dissipates, direct AGN emission can emerge, potentially transforming LRDs into LBDs and marking the end of a short-lived phase of rapid black hole growth. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2601_10573 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Origins of the UV continuum and Balmer emission lines in Little Red Dots: observational validation of dense gas envelope models enshrouding the AGN Asada, Yoshihisa Inayoshi, Kohei Fei, Qinyue Fujimoto, Seiji Willott, Chris Astrophysics of Galaxies We present a statistical study on the origins of the UV continuum and narrow/broad emission lines in little red dots (LRDs), presumably involving active galactic nuclei (AGNs). Leveraging all archived JWST/NIRSpec data, we build a sample of 27 spectroscopically-confirmed LRDs at $5<z_{\rm spec}<7.2$, by requiring broad H$α$ emission, blue UV colors, V-shaped continua, and compact morphology. We define a control sample of 7 blue, compact, broad-line AGNs without red optical continua (hereafter little blue dots; LBDs), and examine correlations between rest UV and the narrow/broad H$α$ luminosities in these populations. In LRDs, both narrow and broad H$α$ components are tightly correlated with the UV continuum, and the luminosity ratios are consistent with those in young starburst galaxies. In contrast, the UV to broad H$α$ ratios in LBDs closely match local unobscured AGNs and are statistically different from LRDs. The Ly$α$ occurrence rates and strengths do not differ between LRDs and LBDs and are comparable to normal star-forming galaxies. These results are consistent with a scenario where the central BH in LRDs is enshrouded by a dense opaque gas envelope -- in this model, the UV continuum as well as narrow and even broad H$α$ emissions are not powered by AGNs but predominantly by young massive stars surrounding the envelope, while the envelope radiates as a $\sim 5000$ K blackbody. As the envelope dissipates, direct AGN emission can emerge, potentially transforming LRDs into LBDs and marking the end of a short-lived phase of rapid black hole growth. |
| title | Origins of the UV continuum and Balmer emission lines in Little Red Dots: observational validation of dense gas envelope models enshrouding the AGN |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2601.10573 |