An unambiguous AGN and a Balmer break in an Ultraluminous Little Red Dot at z=4.47 from Ultradeep UNCOVER and All the Little Things Spectroscopy
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| Natura: | Preprint |
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2024
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| author | Labbe, Ivo Greene, Jenny E. Matthee, Jorryt Treiber, Helena Kokorev, Vasily Miller, Tim B. Kramarenko, Ivan Setton, David J. Ma, Yilun Goulding, Andy D. Bezanson, Rachel Naidu, Rohan P. Williams, Christina C. Atek, Hakim Brammer, Gabriel Cutler, Sam E. Chemerynska, Iryna Cloonan, Aidan P. Dayal, Pratika de Graaff, Anna Fudamoto, Yoshinobu Fujimoto, Seiji Furtak, Lukas J. Glazebrook, Karl Heintz, Kasper E. Leja, Joel Marchesini, Danilo Nanayakkara, Themiya Nelson, Erica J. Oesch, Pascal A. Pan, Richard Price, Sedona H. Shivaei, Irene Sobral, David Suess, Katherine A. van Dokkum, Pieter Wang, Bingjie Weaver, John R. Whitaker, Katherine E. Zitrin, Adi |
| author_facet | Labbe, Ivo Greene, Jenny E. Matthee, Jorryt Treiber, Helena Kokorev, Vasily Miller, Tim B. Kramarenko, Ivan Setton, David J. Ma, Yilun Goulding, Andy D. Bezanson, Rachel Naidu, Rohan P. Williams, Christina C. Atek, Hakim Brammer, Gabriel Cutler, Sam E. Chemerynska, Iryna Cloonan, Aidan P. Dayal, Pratika de Graaff, Anna Fudamoto, Yoshinobu Fujimoto, Seiji Furtak, Lukas J. Glazebrook, Karl Heintz, Kasper E. Leja, Joel Marchesini, Danilo Nanayakkara, Themiya Nelson, Erica J. Oesch, Pascal A. Pan, Richard Price, Sedona H. Shivaei, Irene Sobral, David Suess, Katherine A. van Dokkum, Pieter Wang, Bingjie Weaver, John R. Whitaker, Katherine E. Zitrin, Adi |
| contents | We present a detailed exploration of the most optically-luminous Little Red Dot ($L_{Hα}=10^{44}$erg/s, $L_V=10^{45}$erg/s, F444W=22AB) found to date. Located in the Abell 2744 field, source A744-45924 was observed by NIRSpec/PRISM with ultradeep spectroscopy reaching SNR$\sim$100pix$^{-1}$, high-resolution 3-4 micron NIRCam/Grism spectroscopy, and NIRCam Medium Band imaging. The NIRCam spectra reveal high rest-frame EW $W_{Hα,0,broad}>800$Å, broad H$α$ emission (FWHM$\sim$4500 km/s), on top of narrow, complex absorption. NIRSpec data show exceptionally strong rest-frame UV to NIR Fe II emission ($W_{FeII-UV,0}\sim$340Å), N IV]$λλ$1483,1486 and N III]$λ$1750, and broad NIR O I $λ$8446 emission. The spectra unambiguously demonstrate a broad-line region associated with an inferred $M_{BH}\sim10^9M_\odot$ supermassive black hole embedded in dense gas, which might explain a non-detection in ultradeep Chandra X-ray data (>$10\times$ underluminous relative to broad $L_{Hα}$). Strong UV Nitrogen lines suggest supersolar N/O ratios due to rapid star formation or intense radiation near the AGN. The continuum shows a clear Balmer break at rest-frame 3650Å, which cannot be accounted for by an AGN power-law alone. A stellar population model produces an excellent fit with a reddened Balmer break and implying a massive ($M_*\sim8\times10^{10}M_\odot$), old $\sim$500 Myr, compact stellar core, among the densest stellar systems known ($ρ\sim3\times10^6M_\odot$/pc$^2$ for $R_{e,opt}=70\pm10$ pc), and AGN emission with extreme intrinsic EW $W_{Hα,0}\gg$1000Å. However, although high $M_*$ and $M_{BH}$ are supported by evidence of an overdensity containing 40 galaxies at $z=4.41-4.51$, deep high-resolution spectroscopy is required to confirm stellar absorption and rule out that dense gas around the AGN causes the Balmer break instead. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2412_04557 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | An unambiguous AGN and a Balmer break in an Ultraluminous Little Red Dot at z=4.47 from Ultradeep UNCOVER and All the Little Things Spectroscopy Labbe, Ivo Greene, Jenny E. Matthee, Jorryt Treiber, Helena Kokorev, Vasily Miller, Tim B. Kramarenko, Ivan Setton, David J. Ma, Yilun Goulding, Andy D. Bezanson, Rachel Naidu, Rohan P. Williams, Christina C. Atek, Hakim Brammer, Gabriel Cutler, Sam E. Chemerynska, Iryna Cloonan, Aidan P. Dayal, Pratika de Graaff, Anna Fudamoto, Yoshinobu Fujimoto, Seiji Furtak, Lukas J. Glazebrook, Karl Heintz, Kasper E. Leja, Joel Marchesini, Danilo Nanayakkara, Themiya Nelson, Erica J. Oesch, Pascal A. Pan, Richard Price, Sedona H. Shivaei, Irene Sobral, David Suess, Katherine A. van Dokkum, Pieter Wang, Bingjie Weaver, John R. Whitaker, Katherine E. Zitrin, Adi Astrophysics of Galaxies We present a detailed exploration of the most optically-luminous Little Red Dot ($L_{Hα}=10^{44}$erg/s, $L_V=10^{45}$erg/s, F444W=22AB) found to date. Located in the Abell 2744 field, source A744-45924 was observed by NIRSpec/PRISM with ultradeep spectroscopy reaching SNR$\sim$100pix$^{-1}$, high-resolution 3-4 micron NIRCam/Grism spectroscopy, and NIRCam Medium Band imaging. The NIRCam spectra reveal high rest-frame EW $W_{Hα,0,broad}>800$Å, broad H$α$ emission (FWHM$\sim$4500 km/s), on top of narrow, complex absorption. NIRSpec data show exceptionally strong rest-frame UV to NIR Fe II emission ($W_{FeII-UV,0}\sim$340Å), N IV]$λλ$1483,1486 and N III]$λ$1750, and broad NIR O I $λ$8446 emission. The spectra unambiguously demonstrate a broad-line region associated with an inferred $M_{BH}\sim10^9M_\odot$ supermassive black hole embedded in dense gas, which might explain a non-detection in ultradeep Chandra X-ray data (>$10\times$ underluminous relative to broad $L_{Hα}$). Strong UV Nitrogen lines suggest supersolar N/O ratios due to rapid star formation or intense radiation near the AGN. The continuum shows a clear Balmer break at rest-frame 3650Å, which cannot be accounted for by an AGN power-law alone. A stellar population model produces an excellent fit with a reddened Balmer break and implying a massive ($M_*\sim8\times10^{10}M_\odot$), old $\sim$500 Myr, compact stellar core, among the densest stellar systems known ($ρ\sim3\times10^6M_\odot$/pc$^2$ for $R_{e,opt}=70\pm10$ pc), and AGN emission with extreme intrinsic EW $W_{Hα,0}\gg$1000Å. However, although high $M_*$ and $M_{BH}$ are supported by evidence of an overdensity containing 40 galaxies at $z=4.41-4.51$, deep high-resolution spectroscopy is required to confirm stellar absorption and rule out that dense gas around the AGN causes the Balmer break instead. |
| title | An unambiguous AGN and a Balmer break in an Ultraluminous Little Red Dot at z=4.47 from Ultradeep UNCOVER and All the Little Things Spectroscopy |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2412.04557 |