2025MNRAS.538..327W

We use H I data from the FAST Extended Atlas of Selected Targets Survey (FEASTS) to study the interplay between gas and star formation of galaxies in interacting systems. We build control and mock H I discs and parametrize H I disorder by a series of disorder parameters, describing the piling, clumpiness, and expansion of HH I. We find that interacting galaxies have higher HH I disorder described by almost all disorder parameters. Systems with comparable stellar masses and small relative velocities tend to have stronger expansion and clumpiness of H I. At a given stellar mass, decreased H I and total neutral gas mass and suppressed star formation rate of secondary galaxies are correlated with most disorder parameters. For primary galaxies, H I and total neutral gas deficiency correlate with more H I piling at two ends of the system outside H I discs but not with the expansion or clumpiness of H I. We also find that the H I surface densities of both primary and secondary galaxies are lower within the H I discs and higher outside compared to the control galaxies. Our results suggest that while all the disorder parameters quantify the interaction strength almost equally well, they have different sensitivities in tracing star formation rate and gas mass enhancements. They also imply that while gas removal likely dominates the tidal effects on secondary galaxies, primary galaxies experience more complex situation that are possibly related to gas depletion and accretion happening at different interaction stages.