The scaling relation between baryonic mass and stellar disc size of morphologically late-type galaxies

TL;DR

This paper establishes a fundamental power-law relation between baryonic mass and stellar disc size in late-type galaxies, revealing insights into galaxy structure and the limitations of stellar mass as a tracer in gas-rich systems.

Contribution

It presents the first comprehensive analysis of the baryonic mass-size relation for late-type galaxies, highlighting its fundamental nature and implications for galaxy structure understanding.

Findings

Baryonic mass-size relation is a single power-law across three orders of magnitude.

Scatter in size at fixed baryonic mass remains nearly constant with no outliers.

Stellar mass-size relation deviations are explained by baryonic content, especially in gas-rich galaxies.

Abstract

Here I report the scaling relation between the baryonic masses and the scale lengths of stellar discs from $\sim$1000 morphologically late-type galaxies. The baryonic mass-size relation is a single power-law $R_\ast \propto M_b^{0.38}$ across $\sim$3 orders of magnitude in baryonic mass. The scatter in size at fixed baryonic mass is nearly constant and there is essentially no outlier. The baryonic mass-size relation provides a more fundamental description of the structure of the discs than the stellar mass-size relation. The slope and the scatter of the stellar mass-size relation can be understood in the context of the baryonic mass-size relation. For gas-rich galaxies, the stars is no longer a good tracer for the baryons. High baryonic mass, gas-rich galaxies appear to be much larger at fixed stellar mass because most of the baryonic content is gas. The stellar mass-size relation thus deviates from the power law baryonic relation and the scatter increases at the low stellar mass end. Those extremely gas-rich low-mass galaxies can be classified as Ultra Diffuse Galaxies based on the structure.