Poster Presentation

Physical Origin of Low-Mass Starburst Galaxies in Protoclusters at Cosmic Noon

Author(s): Hayate Hagiwara, Tadayuki Kodama (Tohoku University), Kazuki Daikuhara (ISAS/JAXA)

Presenter: Hayate Hagiwara (Tohoku University)

The environmental contribution to star formation activity at cosmic noon (z~2) is vigorously debated. It is unclear in particular for low-mass galaxies due to their faintness and dificulty in observations. Recently, Daikuhara et al. (2024) reported the enhanced star formation activities of low-mass galaxies (< 10^9 Msun) in a protocluster compared to the field counterparts at this epoch. There are mainly two environmental factors boosting the star formation, mergers/interactions and cold gas accretion along the surrounding filaments, yet their relative imporatence and physical interpretation are yet lacking and hard to verify from observations.
Therefore, we use the IllustrisTNG (Nelson et al. 2019) simulation to investigate the environmental dependence of star formation activities and their physical origins. We classified low-mass galaxies (M* = 10^{8-9} Msun) at z=2 based on their star formation activities by deviation from the star forming main sequence and environments by distance to the 5th-nearest neighbor and compared their properties. We find that the star formation activities of low-mass galaxies strongly depend on their environments, with higher fraction of starbuest galaxies in higher-density environment. Moreover, most of those low-mass starburst galaxies in high-density environemnt experienced recent major mergers within ~150 Myr, suggesting enhanced interactions in high-density environment may induce the starburst. We will also discuss the connection to the relatively inactively star forming galaxies.