WALLABY Pre-Pilot Survey: the effects of angular momentum and environment on the Hi gas and star formation properties of galaxies in the Eridanus supergroup

We use high-resolution ASKAP observations of galaxies in the Eridanus supergroup to study their HI, angular momentum, and star formation properties, as part of the WALLABY pre-pilot survey efforts. The Eridanus supergroup is composed of three sub-groups in the process ofmerging to form a cluster. The main focus of this study is the Eridanus (or NGC 1395) sub-group. The baryonic specific angular momentum - baryonic mass (j(b)-M-b) relation for the Eridanus galaxies is observed to be an unbroken power law of the form j(b) alpha M-b(0.57 +/- 0.05), with a scatter of similar to 0.10 +/- 0.01 dex, consistent with previous works. We examine the relation between the atomic gas fraction, f(atm), and the integrated atomic disc stability parameter q (the f(atm)-q relation), and find that the Eridanus galaxies deviate significantly from the relation owing to environmental processes such as tidal interactions and ram pressure affecting their HI gas. We find that a majority of the Eridanus galaxies are HI deficient compared to normal star-forming galaxies in the field. We also find that the star formation among the Eridanus galaxies may be suppressed owing to their environment, thus hinting at significant levels of pre-processing within the Eridanus sub-group, even before the galaxies have entered a cluster-like environment.

Automated summary

Using high-resolution ASKAP observations of galaxies in the Eridanus supergroup, we studied their HI, angular momentum, and star formation properties, finding consistency with previous works. Environmental processes, such as tidal interactions, were found to significantly impact the relationship between atomic gas fraction and integrated atomic disc stability parameter in Eridanus galaxies. The majority of Eridanus galaxies were also found to be HI deficient compared to normal star-forming galaxies in the field, with indications of suppression in star formation due to their environment.