Rotational Dynamics and Star Formation in the Nearby Dwarf Galaxy NGC 5238

TL;DR

This study provides detailed HI spectral line imaging of the nearby dwarf galaxy NGC 5238, revealing its asymmetric gas distribution, complex kinematics, and relationship with star formation, contributing to understanding low-mass galaxy dynamics.

Contribution

First spatially resolved analysis of NGC 5238's neutral gas distribution and kinematics, linking HI properties with star formation in a low-mass galaxy.

Findings

HI disk is asymmetric with crescent-shaped high-density regions

Neutral gas shows complex kinematics with a rotational velocity of 31 km/s

NGC 5238's properties are consistent with the baryonic Tully-Fisher relation

Abstract

We present new HI spectral line images of the nearby low-mass galaxy NGC 5238, acquired with the Karl G. Jansky Very Large Array (VLA). Located at a distance of 4.51+/-0.04 Mpc, NGC 5238 is an actively star-forming galaxy with widespread H-alpha and UV continuum emission. The source is included in many ongoing and recent nearby galaxy surveys, but until this work the spatially resolved qualities of its neutral interstellar medium have remained unstudied. Our HI images resolve the disk on physical scales of ~400 pc, allowing us to undertake a detailed comparative study of the gaseous and stellar components. The HI disk is asymmetric in the outer regions, and the areas of high HI mass surface density display a crescent-shaped morphology that is slightly offset from the center of the stellar populations. The HI column density exceeds 10^21 cm^-2 in much of the disk. We quantify the degree of co-spatiality of dense HI gas and sites of ongoing star formation as traced by far-UV and H-alpha emission. The neutral gas kinematics are complex; using a spatially-resolved position-velocity analysis, we infer a rotational velocity of 31+/-5 km/s. We place NGC 5238 on the baryonic Tully-Fisher relation and contextualize the system amongst other low-mass galaxies.