First Characterization of the Neutral ISM in Two Local Volume Dwarf Galaxies

TL;DR

This study presents the first HI spectral line images of two local dwarf galaxies, revealing their gas distribution, star formation regions, and dark matter content, and compares their properties.

Contribution

It provides the first detailed HI imaging and analysis of UGC11411 and UGC8245, highlighting differences in their dark matter halos and star formation activity.

Findings

UGC11411 has a more massive dark matter halo than UGC8245.

Star formation correlates with high HI surface density regions.

Both galaxies exhibit negative peculiar velocities linked to nearby galaxy flows.

Abstract

We present the first HI spectral line images of the nearby, star-forming dwarf galaxies UGC11411 and UGC 8245, acquired as part of the "Observing for University Classes" program with the Karl G. Jansky Very Large Array (VLA). These low-resolution images localize the HI gas and reveal the bulk kinematics of each system. Comparing with HST broadband and ground-based H{\alpha} imaging, we find that the ongoing star formation in each galaxy is associated with the highest HI mass surface density regions. UGC 8245 has a much lower current star formation rate than UGC 11411, which harbors very high surface brightness H{\alpha} emission in the inner disk and diffuse, lower surface brightness nebular gas that extends well beyond the stellar disk as traced by HST. We measure the dynamical masses of each galaxy and find that the halo of UGC 11411 is more than an order of magnitude more massive than the halo of UGC 8245, even though the HI and stellar masses of the sources are similar. We show that UGC8245 shares similar physical properties with other well-studied low-mass galaxies, while UGC11411 is more highly dark matter dominated. Both systems have negative peculiar velocities that are associated with a coherent flow of nearby galaxies at high supergalactic latitude.