Gas dynamics and star formation in NGC 6822

TL;DR

This study analyzes the gas kinematics and star formation in NGC 6822 using advanced Bayesian profile decomposition, revealing that cool-bulk H I gas correlates well with star formation rates and follows the Kennicutt-Schmidt law at low densities.

Contribution

Introduces BAYGAUD, a Bayesian tool for decomposing H I velocity profiles, and applies it to classify gas motions and relate them to star formation in NGC 6822.

Findings

Cool-bulk gas component correlates with star formation rate densities.

Cool-bulk component follows the extended Kennicutt-Schmidt law at low densities.

Bayesian profile decomposition effectively classifies gas motions.

Abstract

We present H I gas kinematics and star formation activities of NGC 6822, a dwarf galaxy located in the Local Group at a distance of ~ 490 kpc. We perform profile decomposition of line-of-sight velocity profiles of the H I data cube (42.4" x 12.0" spatial, corresponding to ~ 100 pc; 1.6 km s$^{-1}$ spectral) taken with the Australia Telescope Compact Array (ATCA). For this, we use a new tool, the so-called BAYGAUD which is based on Bayesian analysis techniques, allowing us to decompose a line-of-sight velocity profile into an optimal number of Gaussian components in a quantitative manner. We classify the decomposed H I gas components of NGC 6822 into cool-bulk, warm-bulk, cool-non-bulk and warm-non-bulk motions with respect to their centroid velocities and velocity dispersions. We correlate their gas surface densities with corresponding star formation rate densities derived using both the GALEX far-ultraviolet and WISE 22 $\mu$m data to examine the resolved Kennicutt-Schmidt (K-S) law for NGC 6822. Of the decomposed H I gas components, the cool-bulk component is likely to better follow the linear extension of the K-S law for molecular hydrogen (H$_2$) at low gas surface densities where H I is not saturated.