Kinematic Analysis of z = 4.3 Galaxies in the SPT2349–56 Protocluster Core

Abstract

SPT2349−56 is a protocluster discovered in the 2500 deg ^2 South Pole Telescope (SPT) survey. In this paper, we study the kinematics of the galaxies found in the core of SPT2349−56 using high-resolution (1.55 kpc spatial resolution at z = 4.303) redshifted [C ii ] 158 μ m data. Using the publicly available code ^3D BAROLO , we analyze the seven far-infrared brightest galaxies within the protocluster core. Based on conventional definitions for the detection of rotating disks, we classify six sources to be rotating disks in an actively star-forming protocluster environment, with weighted mean V _rot / σ _disp = 4.5 ± 1.3. The weighted mean rotation velocity ( V _ro _t ) and velocity dispersion ( σ _disp ) for the sample are 357.1 ± 114.7 km s ^−1 and 43.5 ± 23.5 km s ^−1 , respectively. We also assess the disk stability of the galaxies and find a mean Toomre parameter of Q _T = 0.9 ± 0.3. The galaxies show a mild positive correlation between disk stability and dynamical support. Using the position–velocity maps, we find that five sources further classify as disturbed disks, and one classifies as a strictly rotating disk. Our sample joins several observations at similar redshift with high V / σ values, with the exception that they are morphologically disturbed, kinematically rotating, and interacting galaxies in an extreme protocluster environment.

Keywords

• Galaxies
• Galaxy kinematics
• Protoclusters
• High-redshift galaxies