What boost galaxy mergers in two massive galaxy protoclusters at z = 2.24

Abstract

Characterizing the structural properties of galaxies in high-redshift protoclusters is key to our understanding of the environmental effects on galaxy evolution in the early stages of galaxy and structure formation. In this study, we assess the structural properties of 85 and 87 Halpha emission-line candidates (HAEs) in the densest regions of two massive protoclusters, BOSS1244 and BOSS1542, respectively, using HST H-band imaging data. Our results show a true pair fraction of 22+-5 (33+-6) percent in BOSS1244 (BOSS1542), which yields a merger rate of 0.41+-0.09 (0.52+-0.04) per Gyr for massive HAEs with log (M_*/M_sun) > 10.3. This rate is 1.8 (2.8) times higher than that of the general fields at the same epoch. Our sample of HAEs exhibits half-light radii and Sersic indices that cover a broader range than field star-forming galaxies. Additionally, about 15 percent of the HAEs are as compact as the most massive (log(M_*/M_sun) > 11) spheroid-dominated population. These results suggest that the high galaxy density and cold dynamical state (i.e., velocity dispersion of <400 km/s) are key factors that drive galaxy mergers and promote structural evolution in the two protoclusters. Our findings also indicate that both the local environment (on group scales) and the global environment play essential roles in shaping galaxy morphologies in protoclusters. This is evident in the systematic differences observed in the structural properties of galaxies between BOSS1244 and BOSS1542.

20 pages, 5 figures, 1 table. Accepted for publication in MNRAS

References in corpus (33)

• Cold streams in early massive hot haloes as the main mode of galaxy formation
• 3D-HST+CANDELS: The Evolution of the Galaxy Size-Mass Distribution since $z=3$
• Compaction and Quenching of High-z Galaxies in Cosmological Simulations: Blue and Red Nuggets
• Galaxy Merger Morphologies and Time-Scales from Simulations of Equal-Mass Gas-Rich Disc Mergers
• Bimodal gas accretion in the Horizon-MareNostrum galaxy formation simulation
• A fitting formula for the merger timescale of galaxies in hierarchical clustering
• A calibration of the relation between the abundance of close galaxy pairs and the rate of galaxy mergers
• Evolution of the Color-Magnitude Relation in Galaxy Clusters at z ~1 from the ACS Intermediate Redshift Cluster Survey
• Observational constraints on the merger history of galaxies since $z\approx 6$: Probabilistic galaxy pair counts in the CANDELS fields
• Ongoing Assembly of Massive Galaxies by Major Merging in Large Groups and Clusters from the SDSS
• GALAPAGOS: From Pixels to Parameters
• Gas filaments of the cosmic web located around active galaxies in a proto-cluster
• The Luminosity Dependence of the Galaxy Merger Rate
• Major Merging History in CANDELS. I. Evolution of the Incidence of Massive Galaxy-Galaxy Pairs from z=3 to z~0
• On the lifetime of merger features of equal-mass disk mergers
• LoCuSS: Pre-processing in galaxy groups falling into massive galaxy clusters at z=0.2
• HST/WFC3 grism observations of $z\sim 1$ clusters: The cluster vs. field stellar mass-size relation and evidence for size growth of quiescent galaxies from minor mergers
• The merger and assembly histories of Milky Way- and M31-like galaxies with TNG50: disk survival through mergers
• The Late Stellar Assembly of Massive Cluster Galaxies Via Major Merging
• Galaxy evolution in protoclusters
• The effects of the cluster environment on the galaxy mass-size relation in MACSJ J1206.2-0847
• The Differential Size Growth of Field and Cluster Galaxies at z=2.1 Using the ZFOURGE Survey
• Accretion of Galaxy Groups into Galaxy Clusters
• Galaxy Merger Candidates in High-Redshift Cluster Environments
• Galaxy Merger Fractions in Two Clusters at $z\sim 2$ Using the Hubble Space Telescope
• Evidence for a gas-rich major merger in a proto-cluster at z=2.5
• The Properties of Hα Emission-Line Galaxies at z = 2.24
• Understanding large-scale structure in the SSA22 protocluster region using cosmological simulations
• On the Nature of AGN and Star Formation Enhancement in the $z=3.1$ SSA22 Protocluster: The HST WFC3 IR View
• The Three Hundred project: Galaxy groups do not survive cluster infall
• The buildup of galaxies and their spheroids: the contributions of mergers, disc instabilities and star formation
• The Three Hundred project: connection between star formation quenching and dynamical evolution in and around simulated galaxy clusters
• Galactic Disk Formation and the Angular Momentum Problem

Cited by in corpus (1)

• Fast SMBH growth in the SPT2349--56 protocluster at $z=4.3$