Speaker
Description
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. We assess the structural properties of H$\alpha$ emission-line candidates (HAEs) in the densest regions of massive protoclusters at z=2-3, using HST $H$-band imaging data. Our results show the pair fraction of protocluster galaxies yields to higher merger rate for massive HAEs with $\log (M_\ast/{\rm M}_\odot) \ge 10.3$, compared with field galaxies at the same epoch. Meanwhile, we note that the half-light radii and Sersic indices for protocluster HAEs cover a broader range than field star-forming galaxies, suggesting that the high galaxy density and cold dynamical state (i.e., velocity dispersion) are key factors that drive galaxy mergers and promote structural evolution in 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 among different protoclusters.
