Gas Dynamics and Star Formation in NGC 6822

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″ × 12.0″ spatial, corresponding to ∼100 pc; 1.6 km s −1 spectral) taken with the Australia Telescope Compact Array. 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 μ 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.