The effect of ISM turbulence on the gravitational instability of galactic discs

TL;DR

This study examines how turbulence in the interstellar medium influences the gravitational stability of galactic discs, revealing its role in transitioning instability phases and promoting star-driven instabilities in different disc regions.

Contribution

It introduces a model incorporating ISM turbulence effects into galactic disc stability analysis and applies it to observational data from THINGS.

Findings

Turbulence significantly affects inner and outer disc stability.

It causes a transition between two instability regimes in the inner disc.

Outer disc becomes more susceptible to star-driven instabilities.

Abstract

We investigate the gravitational instability of galactic discs, treating stars and cold interstellar gas as two distinct components, and taking into account the phenomenology of turbulence in the interstellar medium (ISM), i.e. the Larson-type scaling relations observed in the molecular and atomic gas. Besides deriving general properties of such systems, we analyse a large sample of galaxies from The HI Nearby Galaxy Survey (THINGS), and show in detail how interstellar turbulence affects disc instability in star-forming spirals. We find that turbulence has a significant effect on both the inner and the outer regions of the disc. In particular, it drives the inner gas disc to a regime of transition between two instability phases and makes the outer disc more prone to star-dominated instabilities.