TY - JOUR

T1 - Starbursts with suppressed velocity dispersion revealed in a forming cluster at z & x2006;& x2004;=& x2004;& x2006;2.51

AU - Xiao, M. -Y.

AU - Wang, T.

AU - Elbaz, D.

AU - Iono, D.

AU - Lu, X.

AU - Bing, L. -J.

AU - Daddi, E.

AU - Magnelli, B.

AU - Gomez-Guijarro, C.

AU - Bournaud, F.

AU - Gu, Q. -S.

AU - Jin, S.

AU - Valentino, F.

AU - Zanella, A.

AU - Gobat, R.

AU - Martin, S.

AU - Brammer, G.

AU - Kohno, K.

AU - Schreiber, C.

AU - Ciesla, L.

AU - Yu, X. -L.

AU - Okumura, K.

PY - 2022/8/4

Y1 - 2022/8/4

N2 - One of the most prominent features of galaxy clusters is the presence of a dominant population of massive ellipticals in their cores. Stellar archaeology suggests that these gigantic beasts assembled most of their stars in the early Universe via starbursts. However, the role of dense environments and their detailed physical mechanisms in triggering starburst activities remain unknown. Here we report spatially resolved Atacama Large Millimeter/submillimeter Array (ALMA) observations of the CO J & x2004;=& x2004;3-2 emission line, with a resolution of about 2.5 kpc, toward a forming galaxy cluster core with starburst galaxies at z & x2004;=& x2004;2.51. In contrast to starburst galaxies in the field often associated with galaxy mergers or highly turbulent gaseous disks, our observations show that the two starbursts in the cluster exhibit dynamically cold (rotation-dominated) gas-rich disks. Their gas disks have extremely low velocity dispersion (sigma(0)& x2004;similar to & x2004;20-30 km s(-1)), which is three times lower than their field counterparts at similar redshifts. The high gas fraction and suppressed velocity dispersion yield gravitationally unstable gas disks, which enables highly efficient star formation. The suppressed velocity dispersion, likely induced by the accretion of corotating and coplanar cold gas, might serve as an essential avenue to trigger starbursts in massive halos at high redshifts.

AB - One of the most prominent features of galaxy clusters is the presence of a dominant population of massive ellipticals in their cores. Stellar archaeology suggests that these gigantic beasts assembled most of their stars in the early Universe via starbursts. However, the role of dense environments and their detailed physical mechanisms in triggering starburst activities remain unknown. Here we report spatially resolved Atacama Large Millimeter/submillimeter Array (ALMA) observations of the CO J & x2004;=& x2004;3-2 emission line, with a resolution of about 2.5 kpc, toward a forming galaxy cluster core with starburst galaxies at z & x2004;=& x2004;2.51. In contrast to starburst galaxies in the field often associated with galaxy mergers or highly turbulent gaseous disks, our observations show that the two starbursts in the cluster exhibit dynamically cold (rotation-dominated) gas-rich disks. Their gas disks have extremely low velocity dispersion (sigma(0)& x2004;similar to & x2004;20-30 km s(-1)), which is three times lower than their field counterparts at similar redshifts. The high gas fraction and suppressed velocity dispersion yield gravitationally unstable gas disks, which enables highly efficient star formation. The suppressed velocity dispersion, likely induced by the accretion of corotating and coplanar cold gas, might serve as an essential avenue to trigger starbursts in massive halos at high redshifts.

KW - galaxies

KW - formation

KW - high-redshift

KW - clusters

KW - general

KW - evolution

KW - ISM

KW - COSMIC STAR-FORMATION

KW - MOLECULAR GAS MASSES

KW - INTERSTELLAR-MEDIUM

KW - MAIN-SEQUENCE

KW - SPECTROSCOPIC SURVEY

KW - SCALING RELATIONS

KW - DUSTY STARBURSTS

KW - MASSIVE GALAXIES

KW - ROTATION CURVES

KW - DEPLETION TIME

U2 - 10.1051/0004-6361/202142843

DO - 10.1051/0004-6361/202142843

M3 - Journal article

VL - 664

JO - Astronomy & Astrophysics

JF - Astronomy & Astrophysics

SN - 0004-6361

M1 - A63

ER -