Invited Presentation

ALMA/ACA CO survey of the IC 1459 and NGC 4636 groups: environmental effects on the molecular gas of group galaxies

Author(s): Bumhyun Lee (Korea Astronomy and Space Science Institute)

Presenter: Bumhyun Lee (Korea Astronomy and Space Science Institute)

At least half of the local galaxies reside in galaxy groups, which indicates that the group environment is the common place where galaxies evolve. In addition, a substantial fraction of cluster galaxies is already quenched in the group environment before they enter the galaxy cluster, which is known as “preprocessing”. Therefore, it is important to probe how significantly galaxies are affected by group environmental processes, in order to obtain a better understanding of galaxy evolution. We carried out a new CO imaging survey for 31 group galaxies in the IC 1459 and NGC 4636 groups, using the Atacama Compact Array, to study the effect of the group environment on the molecular gas properties and the star formation activity. With our resolved CO data, combined with high-resolution H I images (ASKAP and VLA), we find asymmetric CO and/or H I distributions in the galaxies of our group sample. In addition, compared to isolated galaxies, group members have relatively low molecular gas fractions and low star formation rates. These results suggest that the group environment can change the properties of cold gas components and star formation in group galaxies, and thus can play a key role in galaxy evolution. This work is published in Lee et al. 2022, ApJS, 262, 31.