Structure, mass and stability of galactic disks

TL;DR

This review discusses the structure, mass distribution, and stability of galactic disks, highlighting recent progress in understanding their dynamics, dark matter implications, and features like disk truncations.

Contribution

It synthesizes recent findings on stellar disk dynamics, HI layer flaring, and disk truncations, emphasizing the non-maximal nature and local stability of galactic disks.

Findings

Disks are generally not 'maximal' and have lower M/L ratios.

Galactic disks are locally stable according to Toomre's Q criterion.

Flaring of HI layers provides insights into dark matter presence.

Abstract

In this review I concentrate on three areas related to structure of disks in spiral galaxies. First I will review the work on structure, kinematics and dynamics of stellar disks. Next I will review the progress in the area of flaring of HI layers. These subjects are relevant for the presence of dark matter and lead to the conclusion that disk are in general not `maximal', have lower M/L ratios than previously suspected and are locally stable w.r.t. Toomre's Q criterion for local stability. I will end with a few words on `truncations' in stellar disks.