2024/10/19 by Behnam Darvish, Darvish, Behnam, Nima Chartab +13
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena #Stellar, planetary, and galactic studies
paper · pdf · doi:10.48550/arxiv.2410.15177
openalex publication_date 2024/10/19 · openalex created_date 2024/11/06 · openalex updated_date 2026/07/28
We spectroscopically confirm a new protocluster in the COSMOS field at z=2.24430 with Keck/MOSFIRE, dubbed CC2.2B, which is in the immediate vicinity of CC2.2A protocluster, originally presented in \citeDarvish20. CC2.2B and CC2.2A centroids are separated by ∼5.5 Mpc(angular) and ∼16 comoving Mpc(radial). CC2.2B and CC2.2A have similar properties, with CC2.2B having a line-of-sight velocity dispersion and estimated total mass of σlos=693±65 km s-1 and Mtotal=(∼2-3)×1014 M\odot, respectively. These two similar overdensities are likely still in the merging process and will likely collapse into a more massive structure at lower redshifts. We combine CC2.2A and CC2.2B data to investigate the role of high-z protocluster environments on the dynamics of star-forming (SF) galaxies compared to a similarly selected field sample. We find that on average, protocluster SF galaxies have ∼0.1 dex (at ∼1.8σ significance) lower gas velocity dispersions, ∼0.2 dex (at ∼2.2σ significance) lower dynamical masses, and ∼0.2 dex lower dynamical-to-stellar mass ratio than the field SF galaxies. We argue that galaxy harassment and galaxy-galaxy interactions can potentially explain these differences. We also find a factor of ∼2-3 lower scatter around the mean σ-M*, Mdyn-M*, and Mdyn/M* vs. M* relations for protocluster SF galaxies than the field. This could be due to a more uniform formation for protocluster galaxies than their field counterparts. Our results have potential implications for the physics of preprocessing in early environments.