Massive Galaxy Mergers Have Distinctive Global HI Profiles

TL;DR

This study investigates how galaxy mergers affect the global 21 cm HI emission-line profiles, revealing that mergers tend to produce more single-peaked profiles and velocity deviations, providing insights into gas dynamics during interactions.

Contribution

The paper introduces a new method to quantify HI profiles and demonstrates that galaxy mergers have distinctive HI profile features compared to non-mergers.

Findings

Mergers have a higher proportion of single-peaked HI profiles.

Mergers show greater deviations of HI central velocity from systemic velocity.

HI asymmetry is not significantly increased in mergers.

Abstract

The global 21 cm HI emission-line profile of a galaxy encodes valuable information on the spatial distribution and kinematics of the neutral atomic gas. Galaxy interactions significantly influence the HI disk and imprint observable features on the integrated HI line profile. In this work, we study the neutral atomic gas properties of galaxy mergers selected from the Great Observatories All-sky LIRG Survey. The HI spectra come from new observations with the Five-hundred-meter Aperture Spherical Telescope and from a collection of archival data. We quantify the HI profile of the mergers with a newly developed method that uses the curve-of-growth of the line profile. Using a control sample of non-merger galaxies carefully selected to match the stellar mass of the merger sample, we show that mergers have a larger proportion of single-peaked HI profiles, as well as a greater tendency for the HI central velocity to deviate from the systemic optical velocity of the galaxy. By contrast, the HI profiles of mergers are not significantly more asymmetric than those of non-mergers.