COSMOS2020: Discovery of a Protocluster of Massive Quiescent Galaxies at z = 2.77
Protoclusters of galaxies have been found in the last quarter-century. However, most of them have been found through the overdensity of star-forming galaxies, and there have been no known structures identified by more than two spectroscopically confirmed quiescent galaxies at z > 2.5. In this let...
| Main Authors: | , , , , , , , , , , , |
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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 |
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| Online Access: | https://doi.org/10.3847/2041-8213/acb49b |
| _version_ | 1827830887690010624 |
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| author | Kei Ito Masayuki Tanaka Francesco Valentino Sune Toft Gabriel Brammer Katriona M. L. Gould Olivier Ilbert Nobunari Kashikawa Mariko Kubo Yongming Liang Henry J. McCracken John R. Weaver |
| author_facet | Kei Ito Masayuki Tanaka Francesco Valentino Sune Toft Gabriel Brammer Katriona M. L. Gould Olivier Ilbert Nobunari Kashikawa Mariko Kubo Yongming Liang Henry J. McCracken John R. Weaver |
| author_sort | Kei Ito |
| collection | DOAJ |
| description | Protoclusters of galaxies have been found in the last quarter-century. However, most of them have been found through the overdensity of star-forming galaxies, and there have been no known structures identified by more than two spectroscopically confirmed quiescent galaxies at z > 2.5. In this letter, we report the discovery of an overdense structure of massive quiescent galaxies with the spectroscopic redshift z = 2.77 in the COSMOS field, QO-1000. We first photometrically identify this structure as a 4.2 σ overdensity with 14 quiescent galaxies in 7 × 4 pMpc ^2 from the COSMOS2020 catalog. We then securely confirm the spectroscopic redshifts of four quiescent galaxies by detecting multiple Balmer absorption lines with Keck/MOSFIRE. All the spectroscopically confirmed members are massive ( $\mathrm{log}({M}_{\star }/{M}_{\odot })\gt 11.0$ ) and located in a narrow redshift range (2.76 < z < 2.79). Moreover, three of them are in the 1 × 1 pMpc ^2 in the transverse direction at the same redshift ( z = 2.760–2.763). Such a concentration of four spectroscopically confirmed quiescent galaxies implies that QO-1000 is >68 times denser than the general field. In addition, we confirm that they form a red sequence in the J − K _s color. This structure’s halo mass is estimated as $\mathrm{log}({M}_{\mathrm{halo}}/{M}_{\odot })\gt 13.2$ from its stellar mass. Similar structures found in the IllustrisTNG simulation are expected to evolve into massive galaxy clusters with $\mathrm{log}({M}_{\mathrm{halo}}/{M}_{\odot })\geqslant 14.8$ at z = 0. These results suggest that QO-1000 is a more mature protocluster than the other known protoclusters. It is likely in a transition phase between star-forming protoclusters and quenched galaxy clusters. |
| first_indexed | 2024-03-12T04:35:47Z |
| format | Article |
| id | doaj.art-31eaab03446943839cb9c24304293849 |
| institution | Directory Open Access Journal |
| issn | 2041-8205 |
| language | English |
| last_indexed | 2024-03-12T04:35:47Z |
| publishDate | 2023-01-01 |
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| series | The Astrophysical Journal Letters |
| spelling | doaj.art-31eaab03446943839cb9c243042938492023-09-03T09:55:28ZengIOP PublishingThe Astrophysical Journal Letters2041-82052023-01-019451L910.3847/2041-8213/acb49bCOSMOS2020: Discovery of a Protocluster of Massive Quiescent Galaxies at z = 2.77Kei Ito0https://orcid.org/0000-0002-9453-0381Masayuki Tanaka1https://orcid.org/0000-0002-5011-5178Francesco Valentino2https://orcid.org/0000-0001-6477-4011Sune Toft3https://orcid.org/0000-0003-3631-7176Gabriel Brammer4https://orcid.org/0000-0003-2680-005XKatriona M. L. Gould5https://orcid.org/0000-0003-4196-5960Olivier Ilbert6https://orcid.org/0000-0002-7303-4397Nobunari Kashikawa7https://orcid.org/0000-0003-3954-4219Mariko Kubo8https://orcid.org/0000-0002-7598-5292Yongming Liang9https://orcid.org/0000-0002-2725-302XHenry J. McCracken10https://orcid.org/0000-0002-9489-7765John R. Weaver11https://orcid.org/0000-0003-1614-196XDepartment of Astronomy, School of Science, The University of Tokyo , 7-3-1, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan ; kei.ito@astron.s.u-tokyo.ac.jp, kei.ito.astro@gmail.comNational Astronomical Observatory of Japan , 2-21-1 Osawa, Mitaka, Tokyo, 181-8588, Japan; Department of Astronomical Science, The Graduate University for Advanced Studies , SOKENDAI, 2-21-1 Osawa, Mitaka, Tokyo, 181-8588, JapanCosmic Dawn Center (DAWN) , Denmark; Niels Bohr Institute, University of Copenhagen , Jagtvej 128, DK-2200 Copenhagen N, DenmarkCosmic Dawn Center (DAWN) , Denmark; Niels Bohr Institute, University of Copenhagen , Jagtvej 128, DK-2200 Copenhagen N, DenmarkCosmic Dawn Center (DAWN) , Denmark; Niels Bohr Institute, University of Copenhagen , Jagtvej 128, DK-2200 Copenhagen N, DenmarkCosmic Dawn Center (DAWN) , Denmark; Niels Bohr Institute, University of Copenhagen , Jagtvej 128, DK-2200 Copenhagen N, DenmarkAix Marseille Univ , CNRS, CNES, LAM, Marseille, FranceDepartment of Astronomy, School of Science, The University of Tokyo , 7-3-1, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan ; kei.ito@astron.s.u-tokyo.ac.jp, kei.ito.astro@gmail.comAstronomical Institute, Tohoku University , Aoba-ku, Sendai 980-8578, JapanInstitute for Cosmic Ray Research, The University of Tokyo , 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8582, JapanInstitut d’Astrophysique de Paris , 98 bis Boulevard Arago, F-75014, Paris, France; Sorbonne Universités , UPMC Univ. Paris 6 et CNRS, UMR 7095, Institut d’Astrophysique de Paris, 98 bis bd Arago, F-75014 Paris, FranceDepartment of Astronomy, University of Massachusetts , Amherst, MA 01003, USAProtoclusters of galaxies have been found in the last quarter-century. However, most of them have been found through the overdensity of star-forming galaxies, and there have been no known structures identified by more than two spectroscopically confirmed quiescent galaxies at z > 2.5. In this letter, we report the discovery of an overdense structure of massive quiescent galaxies with the spectroscopic redshift z = 2.77 in the COSMOS field, QO-1000. We first photometrically identify this structure as a 4.2 σ overdensity with 14 quiescent galaxies in 7 × 4 pMpc ^2 from the COSMOS2020 catalog. We then securely confirm the spectroscopic redshifts of four quiescent galaxies by detecting multiple Balmer absorption lines with Keck/MOSFIRE. All the spectroscopically confirmed members are massive ( $\mathrm{log}({M}_{\star }/{M}_{\odot })\gt 11.0$ ) and located in a narrow redshift range (2.76 < z < 2.79). Moreover, three of them are in the 1 × 1 pMpc ^2 in the transverse direction at the same redshift ( z = 2.760–2.763). Such a concentration of four spectroscopically confirmed quiescent galaxies implies that QO-1000 is >68 times denser than the general field. In addition, we confirm that they form a red sequence in the J − K _s color. This structure’s halo mass is estimated as $\mathrm{log}({M}_{\mathrm{halo}}/{M}_{\odot })\gt 13.2$ from its stellar mass. Similar structures found in the IllustrisTNG simulation are expected to evolve into massive galaxy clusters with $\mathrm{log}({M}_{\mathrm{halo}}/{M}_{\odot })\geqslant 14.8$ at z = 0. These results suggest that QO-1000 is a more mature protocluster than the other known protoclusters. It is likely in a transition phase between star-forming protoclusters and quenched galaxy clusters.https://doi.org/10.3847/2041-8213/acb49bGalaxy evolutionHigh-redshift galaxy clustersGalaxy environmentsGalaxy quenchingQuenched galaxies |
| spellingShingle | Kei Ito Masayuki Tanaka Francesco Valentino Sune Toft Gabriel Brammer Katriona M. L. Gould Olivier Ilbert Nobunari Kashikawa Mariko Kubo Yongming Liang Henry J. McCracken John R. Weaver COSMOS2020: Discovery of a Protocluster of Massive Quiescent Galaxies at z = 2.77 The Astrophysical Journal Letters Galaxy evolution High-redshift galaxy clusters Galaxy environments Galaxy quenching Quenched galaxies |
| title | COSMOS2020: Discovery of a Protocluster of Massive Quiescent Galaxies at z = 2.77 |
| title_full | COSMOS2020: Discovery of a Protocluster of Massive Quiescent Galaxies at z = 2.77 |
| title_fullStr | COSMOS2020: Discovery of a Protocluster of Massive Quiescent Galaxies at z = 2.77 |
| title_full_unstemmed | COSMOS2020: Discovery of a Protocluster of Massive Quiescent Galaxies at z = 2.77 |
| title_short | COSMOS2020: Discovery of a Protocluster of Massive Quiescent Galaxies at z = 2.77 |
| title_sort | cosmos2020 discovery of a protocluster of massive quiescent galaxies at z 2 77 |
| topic | Galaxy evolution High-redshift galaxy clusters Galaxy environments Galaxy quenching Quenched galaxies |
| url | https://doi.org/10.3847/2041-8213/acb49b |
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