# Connecting Clump Sizes in Turbulent Disk Galaxies to Instability Theory

## TL;DR

This study links the sizes of star-forming clumps in turbulent disk galaxies to gravitational instabilities, supporting the violent disk instability model as the mechanism behind clump formation.

## Contribution

It provides observational evidence connecting clump sizes to disk instabilities, using high-resolution imaging and kinematic data in a sample of nearby turbulent galaxies.

## Key findings

- Clump sizes correlate with gas fraction and velocity dispersion ratios.
- Results align with predictions from the violent disk instability model.
- Clump sizes are linked to self-gravitating unstable regions in disks.

## Abstract

In this letter we study the mean sizes of Halpha clumps in turbulent disk galaxies relative to kinematics, gas fractions, and Toomre Q. We use 100~pc resolution HST images, IFU kinematics, and gas fractions of a sample of rare, nearby turbulent disks with properties closely matched to z~1.5-2 main-sequence galaxies (the DYNAMO sample). We find linear correlations of normalized mean clump sizes with both the gas fraction and the velocity dispersion-to-rotation velocity ratio of the host galaxy. We show that these correlations are consistent with predictions derived from a model of instabilities in a self-gravitating disk (the so-called "violent disk instability model"). We also observe, using a two-fluid model for Q, a correlation between the size of clumps and self-gravity driven unstable regions. These results are most consistent with the hypothesis that massive star forming clumps in turbulent disks are the result of instabilities in self-gravitating gas-rich disks, and therefore provide a direct connection between resolved clump sizes and this in situ mechanism.