Little Red Dots or Brown Dwarfs? NIRSpec Discovery of Three Distant Brown Dwarfs Masquerading as NIRCam-selected Highly Reddened Active Galactic Nuclei
Cold, substellar objects such as brown dwarfs have long been recognized as contaminants in color-selected samples of active galactic nuclei (AGNs). In particular, their near- to mid-infrared colors (1–5 μ m) can closely resemble the V-shaped ( f _λ ) spectra of highly reddened accreting supermassive...
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| Format: | Article |
| Language: | English |
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IOP Publishing
2023-01-01
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| Series: | The Astrophysical Journal Letters |
| Subjects: | |
| Online Access: | https://doi.org/10.3847/2041-8213/acfeec |
| _version_ | 1797633599008145408 |
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| author | Danial Langeroodi Jens Hjorth |
| author_facet | Danial Langeroodi Jens Hjorth |
| author_sort | Danial Langeroodi |
| collection | DOAJ |
| description | Cold, substellar objects such as brown dwarfs have long been recognized as contaminants in color-selected samples of active galactic nuclei (AGNs). In particular, their near- to mid-infrared colors (1–5 μ m) can closely resemble the V-shaped ( f _λ ) spectra of highly reddened accreting supermassive black holes (“little red dots”), especially at 6 < z < 7. Recently, a NIRCam-selected sample of little red dots over 45 arcmin ^2 has been followed up with deep NIRSpec multiobject prism spectroscopy through the UNCOVER program. By investigating the acquired spectra, we identify 3 of the 14 followed-up objects as T/Y dwarfs with temperatures between 650 and 1300 K and distances between 0.8 and 4.8 kpc. At ${4.8}_{-0.1}^{+0.6}$ kpc, A2744-BD1 is the most distant brown dwarf discovered to date. We identify the remaining 11 objects as extragalactic sources at z _spec ≳ 5. Given that three of these sources are strongly lensed images of the same AGN (A2744-QSO1), we derive a brown dwarf contamination fraction of 25% in this NIRCam selection of little red dots. We find that in the near-infrared filters, brown dwarfs appear much bluer than the highly reddened AGN, providing an avenue for distinguishing the two and compiling cleaner samples of photometrically selected highly reddened AGN. |
| first_indexed | 2024-03-11T11:56:10Z |
| format | Article |
| id | doaj.art-c15b966c0c694868a996e2bdb08d43ca |
| institution | Directory Open Access Journal |
| issn | 2041-8205 |
| language | English |
| last_indexed | 2024-03-11T11:56:10Z |
| publishDate | 2023-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal Letters |
| spelling | doaj.art-c15b966c0c694868a996e2bdb08d43ca2023-11-08T17:58:09ZengIOP PublishingThe Astrophysical Journal Letters2041-82052023-01-019572L2710.3847/2041-8213/acfeecLittle Red Dots or Brown Dwarfs? NIRSpec Discovery of Three Distant Brown Dwarfs Masquerading as NIRCam-selected Highly Reddened Active Galactic NucleiDanial Langeroodi0https://orcid.org/0000-0001-5710-8395Jens Hjorth1https://orcid.org/0000-0002-4571-2306DARK, Niels Bohr Institute, University of Copenhagen , Jagtvej 128, DK-2200 Copenhagen, Denmark ; danial.langeroodi@nbi.ku.dkDARK, Niels Bohr Institute, University of Copenhagen , Jagtvej 128, DK-2200 Copenhagen, Denmark ; danial.langeroodi@nbi.ku.dkCold, substellar objects such as brown dwarfs have long been recognized as contaminants in color-selected samples of active galactic nuclei (AGNs). In particular, their near- to mid-infrared colors (1–5 μ m) can closely resemble the V-shaped ( f _λ ) spectra of highly reddened accreting supermassive black holes (“little red dots”), especially at 6 < z < 7. Recently, a NIRCam-selected sample of little red dots over 45 arcmin ^2 has been followed up with deep NIRSpec multiobject prism spectroscopy through the UNCOVER program. By investigating the acquired spectra, we identify 3 of the 14 followed-up objects as T/Y dwarfs with temperatures between 650 and 1300 K and distances between 0.8 and 4.8 kpc. At ${4.8}_{-0.1}^{+0.6}$ kpc, A2744-BD1 is the most distant brown dwarf discovered to date. We identify the remaining 11 objects as extragalactic sources at z _spec ≳ 5. Given that three of these sources are strongly lensed images of the same AGN (A2744-QSO1), we derive a brown dwarf contamination fraction of 25% in this NIRCam selection of little red dots. We find that in the near-infrared filters, brown dwarfs appear much bluer than the highly reddened AGN, providing an avenue for distinguishing the two and compiling cleaner samples of photometrically selected highly reddened AGN.https://doi.org/10.3847/2041-8213/acfeecBrown dwarfsT dwarfsY dwarfsActive galactic nuclei |
| spellingShingle | Danial Langeroodi Jens Hjorth Little Red Dots or Brown Dwarfs? NIRSpec Discovery of Three Distant Brown Dwarfs Masquerading as NIRCam-selected Highly Reddened Active Galactic Nuclei The Astrophysical Journal Letters Brown dwarfs T dwarfs Y dwarfs Active galactic nuclei |
| title | Little Red Dots or Brown Dwarfs? NIRSpec Discovery of Three Distant Brown Dwarfs Masquerading as NIRCam-selected Highly Reddened Active Galactic Nuclei |
| title_full | Little Red Dots or Brown Dwarfs? NIRSpec Discovery of Three Distant Brown Dwarfs Masquerading as NIRCam-selected Highly Reddened Active Galactic Nuclei |
| title_fullStr | Little Red Dots or Brown Dwarfs? NIRSpec Discovery of Three Distant Brown Dwarfs Masquerading as NIRCam-selected Highly Reddened Active Galactic Nuclei |
| title_full_unstemmed | Little Red Dots or Brown Dwarfs? NIRSpec Discovery of Three Distant Brown Dwarfs Masquerading as NIRCam-selected Highly Reddened Active Galactic Nuclei |
| title_short | Little Red Dots or Brown Dwarfs? NIRSpec Discovery of Three Distant Brown Dwarfs Masquerading as NIRCam-selected Highly Reddened Active Galactic Nuclei |
| title_sort | little red dots or brown dwarfs nirspec discovery of three distant brown dwarfs masquerading as nircam selected highly reddened active galactic nuclei |
| topic | Brown dwarfs T dwarfs Y dwarfs Active galactic nuclei |
| url | https://doi.org/10.3847/2041-8213/acfeec |
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