# Comparing the Properties of GMCs in M33 from Simulations and Observations

## TL;DR

This study compares simulated and observed molecular cloud properties in M33, finding strong agreement and highlighting the influence of surface density over feedback or simulation specifics.

## Contribution

It demonstrates that molecular cloud properties in M33 are primarily governed by gas surface density, with simulations accurately reproducing observed trends and spectra.

## Key findings

- Good agreement in cloud number and mass between simulations and observations
- Cloud properties depend mainly on gas surface density, not feedback level
- Cloud spectra match well, but depend on detection algorithm and mass range

## Abstract

We compare the properties of clouds in simulated M33 galaxies to those observed in the real M33. We apply a friends of friends algorithm and CPROPS to identify clouds, as well as a pixel by pixel analysis. We obtain very good agreement between the number of clouds, and maximum mass of clouds. Both are lower than occurs for a Milky Way-type galaxy and thus are a function of the surface density, size and galactic potential of M33. We reproduce the observed dependence of molecular cloud properties on radius in the simulations, and find this is due to the variation in gas surface density with radius. The cloud spectra also show good agreement between the simulations and observations, but the exact slope and shape of the spectra depends on the algorithm used to find clouds, and the range of cloud masses included when fitting the slope. Properties such as cloud angular momentum, velocity dispersions and virial relation are also in good agreement between the simulations and observations, but do not necessarily distinguish between simulations of M33 and other galaxy simulations. Our results are not strongly dependent on the level of feedback used here (10 and 20%) although they suggest that 15% feedback efficiency may be optimal. Overall our results suggest that the molecular cloud properties are primarily dependent on the gas and mass surface density, and less dependent on the localised physics such as the details of stellar feedback, or the numerical code used.