The HI Gas Disk Thickness of the Ultra-diffuse Galaxy AGC 242019

TL;DR

This study measures the HI gas disk thickness of the ultra-diffuse galaxy AGC 242019 and finds it similar to dwarf galaxies, providing insights into its formation and feedback processes.

Contribution

It introduces a method to measure HI disk thickness in UDGs and compares AGC 242019's disk to dwarf galaxies, suggesting similar feedback effects.

Findings

HI scale height of AGC 242019 is approximately 537 pc

Flaring angle of the HI disk is about 0.19

AGC 242019's disk thickness is comparable to dwarf irregulars

Abstract

Ultra-diffuse galaxies (UDGs) are as faint as dwarf galaxies but whose sizes are similar to those of spiral galaxies. A variety of formation mechanisms have been proposed, some of which could result in different disk thicknesses. In this study, we measure the radial profile of the HI scale height (h_g) and flaring angle (h_g/R) of AGC 242019 through the joint Poisson-Boltzmann equation based on its well spatially-resolved HI gas maps. The mean HI scale height of AGC 242019 is <h_g> \approx 537.15 \pm 89.4 pc, and the mean flaring angle is <h_g/R> \approx 0.19 \pm 0.03. As a comparison, we also derive the disk thickness for a sample of 14 dwarf irregulars. It is found that the HI disk of AGC 242019 has comparable thickness to dwarfs. This suggests that AGC 242019 is unlikely to experience much stronger stellar feedback than dwarf galaxies, which otherwise leads to a thicker disk for this galaxy.