Interaction-induced HI gas concentration with centrally-enhanced star formation in ALFALFA-SDSS galaxies

TL;DR

This study shows that galaxy interactions increase central HI gas concentration and star formation, with stronger effects in low-mass galaxies, highlighting the role of tidal forces in galaxy evolution.

Contribution

It provides a large-scale statistical analysis linking HI gas concentration and star formation enhancement to galaxy interactions, using the HI profile parameter $K$.

Findings

Higher HI concentration correlates with increased clustering and nearby neighbors.

Tidal interactions cause synchronized increases in gas concentration and star formation.

Central galaxies show stronger gas and star formation enhancements than satellites.

Abstract

We present a statistical analysis for the interaction-induced central concentration of HI gas distributions and its connection with interaction-induced central star formation enhancement, using a large sample of $\sim 10^4$ galaxies from the ALFALFA and SDSS surveys. By adopting the HI profile parameter $K$, an indicator of gas concentration inferred from the integrated 21 cm emission line, we find that galaxies with more centrally concentrated HI (higher $K$ values) or enhanced specific star foramtion rate (sSFR) exhibit significantly stronger clustering and higher probability of hosting a nearby neighbor on scales below $100h^{-1}\mathrm{kpc}$, which is more pronounced in low-mass galaxies. Furthermore, by utilizing the enhancement functions for a sample of galaxy pairs, we directly trace the evolution of HI concentration and sSFR enhancement as a function of projected separation. Our findings indicate that tidal interactions drive a statistical synchrony between the central concentration of atomic gas and the enhancement of central star formation. Gas concentration appears to be a necessary condition for central star formation enhancement in interacting systems at all but the smallest separations. Compared to satellite galaxies, central galaxies exhibit stronger enhancement of gas fraction, gas concentration and sSFR, suggesting the role of environmental regulation.