COSMOS2020: Discovery of a Protocluster of Massive Quiescent Galaxies at z=2.77
Publikation: Bidrag til tidsskrift › Letter › Forskning › fagfællebedømt
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COSMOS2020 : Discovery of a Protocluster of Massive Quiescent Galaxies at z=2.77. / Ito, Kei; Tanaka, Masayuki; Valentino, Francesco; Toft, Sune; Brammer, Gabriel; Gould, Katriona M. L.; Ilbert, Olivier; Kashikawa, Nobunari; Kubo, Mariko; Liang, Yongming; McCracken, Henry J.; Weaver, John R.
I: Astrophysical Journal Letters, Bind 945, Nr. 1, 9, 01.03.2023.Publikation: Bidrag til tidsskrift › Letter › Forskning › fagfællebedømt
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TY - JOUR
T1 - COSMOS2020
T2 - Discovery of a Protocluster of Massive Quiescent Galaxies at z=2.77
AU - Ito, Kei
AU - Tanaka, Masayuki
AU - Valentino, Francesco
AU - Toft, Sune
AU - Brammer, Gabriel
AU - Gould, Katriona M. L.
AU - Ilbert, Olivier
AU - Kashikawa, Nobunari
AU - Kubo, Mariko
AU - Liang, Yongming
AU - McCracken, Henry J.
AU - Weaver, John R.
PY - 2023/3/1
Y1 - 2023/3/1
N2 - 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 sigma overdensity with 14 quiescent galaxies in 7 x 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 (log (M-* M-?) > 11.0) and located in a narrow redshift range (2.76 < z < 2.79). Moreover, three of them are in the 1 x 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 - Ks color. This structure's halo mass is estimated as log(M-halo M-?) > 13.2 from its stellar mass. Similar structures found in the IllustrisTNG simulation are expected to evolve into massive galaxy clusters with log(M-halo M-?) >= 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.
AB - 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 sigma overdensity with 14 quiescent galaxies in 7 x 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 (log (M-* M-?) > 11.0) and located in a narrow redshift range (2.76 < z < 2.79). Moreover, three of them are in the 1 x 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 - Ks color. This structure's halo mass is estimated as log(M-halo M-?) > 13.2 from its stellar mass. Similar structures found in the IllustrisTNG simulation are expected to evolve into massive galaxy clusters with log(M-halo M-?) >= 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.
KW - STAR-FORMATION HISTORIES
KW - HUBBLE-SPACE-TELESCOPE
KW - LARGE-SCALE STRUCTURES
KW - LY-ALPHA EMITTERS
KW - SIMILAR-TO 4
KW - STELLAR MASS
KW - PROTO-CLUSTER
KW - X-RAY
KW - SPECTROSCOPIC CONFIRMATION
KW - PHOTOMETRIC REDSHIFT
U2 - 10.3847/2041-8213/acb49b
DO - 10.3847/2041-8213/acb49b
M3 - Letter
VL - 945
JO - The Astrophysical Journal Letters
JF - The Astrophysical Journal Letters
SN - 2041-8205
IS - 1
M1 - 9
ER -
ID: 340949101