Spiral shocks induced in galactic gaseous disk: hydrodynamic understanding of observational properties of spiral galaxies

TL;DR

This paper models spiral shocks in galactic disks to understand their impact on observable properties like star formation rates and spiral structure, revealing how self-gravity influences galactic dynamics.

Contribution

It introduces a self-similar hydrodynamic model of spiral shocks in self-gravitating galactic disks, linking physical disk properties to observational galaxy features.

Findings

Self-gravity significantly affects spiral shock dynamics.

Observed correlations between pitch angle, shear rate, and star formation rate.

Variations in star formation efficiency explain differences among similar galaxies.

Abstract

We investigate the properties of spiral shocks in a steady, adiabatic, non-axisymmetric, self-gravitating, mass-outflowing accretion disk around a compact object. We obtain the accretion-ejection solutions in a gaseous galactic disk and apply them to the spiral galaxies to investigate the possible physical connections between some galaxy observational quantities. The self-gravitating disk potential is considered following Mestel's (1963) prescription. The spiral shock-induced accretion-ejection solutions are obtained following the point-wise self-similar approach. We observe that the self-gravitating disk profoundly affects the dynamics of the spiral structure of the disk and the properties of the spiral shocks. We find that the observational dispersion between the pitch angle and shear rate and between the pitch angle and star formation rate in spiral galaxies contains some important physical information. There are large differences in star formation rates among galaxies with similar pitch angles, which may be explained by the different star formation efficiencies caused by the distinct galactic ambient conditions.