The relation between specific baryon angular momentum and mass for a sample of nearby low-mass galaxies with resolved HI kinematics

TL;DR

This study examines the relationship between baryon angular momentum and mass in nearby low-mass galaxies, confirming the theoretical $j_b \\propto M_b^{2/3}$ relation with improved data and analysis.

Contribution

It provides new measurements of the $j_b - M_b$ relation for low-mass galaxies, doubling the sample size and confirming the theoretical power-law slope with low-resolution HI data.

Findings

The relation is consistent with $j_b \\propto M_b^{2/3}$.

Results are robust against low-resolution imaging systematics.

Sample includes galaxies with baryon mass dominated by gas.

Abstract

This paper investigates the relationship between specific baryon angular momentum $j_\mathrm{b}$ and baryon mass $M_\mathrm{b}$ for a sample of nearby late-type galaxies with resolved HI kinematics. This work roughly doubles the number of galaxies with $M_\mathrm{b} \lesssim 10^{10}$ $M_{\odot}$ used to study the $j_\mathrm{b} - M_\mathrm{b}$ relation. Most of the galaxies in the sample have their baryon mass dominated by their gas content, thereby offering $j_\mathrm{b}$ and Mb measures that are relatively unaffected by uncertainties arising from the stellar mass-to-light ratio. Measured HI surface density radial profiles together with optical and rotation curve data from the literature are used to derive a best-fit relation given by $j_\mathrm{b}=qM_\mathrm{b}^{\alpha}$, with $\alpha=0.62\pm 0.02$ and $\log_{10}q=-3.35\pm 0.25$. This result is consistent with the $j_\mathrm{b}\propto M_\mathrm{b}^{2/3}$ relation that is theoretically expected and also measured by Obreschkow & Glazebrook (2014) for their full sample of THINGS spiral galaxies, yet differs to their steeper relation found for subsets with fixed bulge fraction. The 30 arcsec spatial resolution of the HI imaging used in this study is significantly lower than that of the THINGS imaging used by Obreschkow & Glazebrook (2014), yet the results presented in this work are clearly shown to contain no significant systematic errors due to the low-resolution imaging.