Molecular Gas and Star Formation in Dwarf Galaxies Observed by the Atacama Large Millimeter/submillimeter Array

TL;DR

This study uses high-resolution ALMA observations to analyze the molecular star formation law and gravitational stability in nearby dwarf galaxies, revealing that star formation processes are similar to those in larger galaxies despite differences in mass and metallicity.

Contribution

It provides the first detailed spatially resolved analysis of the molecular star formation law in dwarf galaxies using ALMA data, showing a universal SFL slope comparable to massive spirals.

Findings

Molecular SFL slope averages around 0.81, consistent with massive spirals.

Radial Toomre Q profiles are near unity, indicating self-regulation.

Star formation governed by similar physics in dwarf and larger galaxies.

Abstract

We present a spatially resolved analysis of the molecular star formation law (SFL) and gravitational instability in a sample of nearby dwarf galaxies (NGC 1035, NGC 4310, NGC 4451, NGC 4701, NGC 5692, and NGC 6106), using high-resolution $^{12}$CO ($J=1\rightarrow0$) data from the Atacama Large Millimeter/submillimeter Array. We estimate the star formation rate (SFR) by combining the Galaxy Evolution Explorer near-ultraviolet and the Wide-field Infrared Survey Explorer 12 $\mu$m imaging data to examine the relationship between molecular gas and SFR densities on scales of several hundred parsecs. We find that the power-law slope of the molecular SFL ranges from 0.62 to 1.08, with an average value of N$=0.81\pm0.18$, increasing to N$=0.87\pm0.05$ when excluding galaxies with poorly constrained CO data. These results are roughly consistent with values observed in massive spiral galaxies, suggesting a universal molecular SFL when analyzed with sufficient resolution and sensitivity. Radial profiles of the Toomre $Q$ parameter remain close to unity across the disks, with minimal radial variation, consistent with a self-regulated star formation model. Our results suggest that, despite their lower mass and metallicity, star formation in dwarf galaxies is governed by the same fundamental physical processes as in larger systems. This highlights the significance of high-resolution molecular gas observations in low-mass galaxies.