Gas dynamics in dwarf galaxies as testbeds for dark matter and galaxy evolution

TL;DR

This review discusses how gas dynamics in dwarf galaxies serve as crucial tests for dark matter models and galaxy evolution, highlighting the extension of dynamical laws to lower mass scales and the tight baryon-dark matter coupling.

Contribution

It synthesizes current understanding of gas dynamics in dwarf galaxies, emphasizing the role of rotation curves, mass models, and the universality of dynamical laws at low masses.

Findings

Dwarf galaxies extend spiral galaxy dynamical laws to lower masses.

Three distinct acceleration scales are identified in galaxy rotation laws.

A tight baryon-dark matter coupling is observed across dwarf galaxies.

Abstract

Dwarf galaxies are ideal laboratories to test dark matter models and alternative theories because their dynamical mass (from observed kinematics) largely outweighs their baryonic mass (from gas and stars). In most star-forming dwarfs, cold atomic gas forms regularly rotating disks extending beyond the stellar component, thus probing the gravitational potential out to the outermost regions. Here I review several aspects of gas dynamics in dwarf galaxies, such as rotation curves, mass models, and noncircular motions. Star-forming dwarfs extend the dynamical laws of spiral galaxies to lower masses, surface densities, and accelerations. The three main dynamical laws of rotation-supported galaxies point to three distinct acceleration scales, which play different physical roles but display the same value, within uncertainties. The small scatter around these dynamical laws implies a tight coupling between baryons and dark matter in galaxies, which will be better understood with next-generation surveys that will enlarge current sample sizes by orders of magnitude.