TY - JOUR

T1 - A galaxy group candidate at z approximate to 3.7 in the COSMOS field

AU - Sillassen, Nikolaj B.

AU - Jin, Shuowen

AU - Magdis, Georgios E.

AU - Daddi, Emanuele

AU - Weaver, John R.

AU - Gobat, Raphael

AU - Kokorev, Vasilii

AU - Valentino, Francesco

AU - Finoguenov, Alexis

AU - Shuntov, Marko

AU - Gomez-Guijarro, Carlos

AU - Coogan, Rosemary

AU - Greve, Thomas R.

AU - Toft, Sune

AU - Sese, David Blanquez

PY - 2022/9/19

Y1 - 2022/9/19

N2 - We report a galaxy group candidate HPC1001 at z approximate to 3.7 in the COSMOS field. This structure was selected as a high galaxy overdensity at z > 3 in the COSMOS2020 catalog. It contains ten candidate members, of which eight are assembled in a 10 '' x 10 '' area with the highest sky density among known protoclusters and groups at z > 3. Four out of ten sources were also detected at 1.2mm with Atacama Large Millimeter Array continuum observations. Photometric redshifts, measured by four independent methods, fall within a narrow range of 3.5 < z < 3.9 and with a weighted average of z = 3.65 +/- 0.07. The integrated far-IR-to-radio spectral energy distribution yields a total UV and IR star formation rate SFR approximate to 900 M-circle dot yr(-1). We also estimated a halo mass of similar to 10(13) M-circle dot for the structure, which at this redshift is consistent with potential cold gas inflow. Remarkably, the most massive member has a specific star formation rate and dust to stellar mass ratio of M-dust/M-* that are both significantly lower than that of star-forming galaxies at this redshift, suggesting that HPC1001 could be a z approximate to 3.7 galaxy group in maturing phase. If confirmed, this would be the earliest structure in maturing phase to date, and an ideal laboratory to study the formation of the earliest quiescent galaxies as well as cold gas accretion in dense environments.

AB - We report a galaxy group candidate HPC1001 at z approximate to 3.7 in the COSMOS field. This structure was selected as a high galaxy overdensity at z > 3 in the COSMOS2020 catalog. It contains ten candidate members, of which eight are assembled in a 10 '' x 10 '' area with the highest sky density among known protoclusters and groups at z > 3. Four out of ten sources were also detected at 1.2mm with Atacama Large Millimeter Array continuum observations. Photometric redshifts, measured by four independent methods, fall within a narrow range of 3.5 < z < 3.9 and with a weighted average of z = 3.65 +/- 0.07. The integrated far-IR-to-radio spectral energy distribution yields a total UV and IR star formation rate SFR approximate to 900 M-circle dot yr(-1). We also estimated a halo mass of similar to 10(13) M-circle dot for the structure, which at this redshift is consistent with potential cold gas inflow. Remarkably, the most massive member has a specific star formation rate and dust to stellar mass ratio of M-dust/M-* that are both significantly lower than that of star-forming galaxies at this redshift, suggesting that HPC1001 could be a z approximate to 3.7 galaxy group in maturing phase. If confirmed, this would be the earliest structure in maturing phase to date, and an ideal laboratory to study the formation of the earliest quiescent galaxies as well as cold gas accretion in dense environments.

KW - Galaxy: evolution

KW - galaxies: high-redshift

KW - submillimeter: galaxies

KW - galaxies: clusters: general

KW - EVOLVING INTERSTELLAR-MEDIUM

KW - STAR-FORMING GALAXIES

KW - SPIDERWEB PROTOCLUSTER

KW - QUIESCENT GALAXIES

KW - DUSTY STARBURSTS

KW - PROTO-CLUSTER

KW - REDSHIFT

KW - EVOLUTION

KW - SELECTION

KW - HERSCHEL

U2 - 10.1051/0004-6361/202244661

DO - 10.1051/0004-6361/202244661

M3 - Journal article

VL - 665

JO - Astronomy & Astrophysics

JF - Astronomy & Astrophysics

SN - 0004-6361

M1 - L7

ER -