# A High-Resolution, Dust-Selected Molecular Cloud Catalogue of M33, the Triangulum Galaxy

## TL;DR

This paper presents a detailed catalogue of 165 Giant Molecular Clouds in M33, analyzing their properties, distribution, and mass function, revealing differences from the Milky Way and insights into cloud formation.

## Contribution

The study provides the first high-resolution dust-selected GMC catalogue for M33, including measurements of dust properties, gas-to-dust ratios, and mass functions, with comparisons to previous CO studies.

## Key findings

- GMCs range from 10^4 to 10^7 solar masses.
- GDR decreases with galactocentric radius, lower than in the Milky Way.
- Mass function slope is steeper than in other local galaxies.

## Abstract

We present a catalogue of Giant Molecular Clouds (GMCs) in M33, extracted from cold dust continuum emission. Our GMCs are identified by computing dendrograms. We measure the spatial distribution of these clouds, and characterise their dust properties. Combining these measured properties with CO(J=2-1) and 21cm HI data, we calculate the gas-to-dust ratio (GDR) of these clouds, and from this compute a total cloud mass. In total, we find 165 GMCs with cloud masses in the range of 10$^4$-10$^7$ M$_\odot$. We find that radially, $\log_{10}(\mathrm{GDR}) = -0.043(\pm0.038) \,\mathrm{R [kpc]} + 1.88(\pm0.15)$, a much lower GDR than found in the Milky Way, and a correspondingly higher $\alpha_{\rm CO}$ factor. The mass function of these clouds follows a slope proportional to M$^{-2.84}$, steeper than many previous studies of GMCs in local galaxies, implying that M33 is poorer at forming massive clouds than other nearby spirals. Whilst we can rule out interstellar pressure as the major contributing factor, we are unable to disentangle the relative effects of metallicity and HI velocity dispersion. We find a reasonably featureless number density profile with galactocentric radius, and weak correlations between galactocentric radius and dust temperature/mass. These clouds are reasonably consistent with Larson's scaling relationships, and many of our sources are co-spatial with earlier CO studies. Massive clouds are identified at large galactocentric radius, unlike in these earlier studies, perhaps indicating a population of CO-dark gas dominated clouds at these larger distances.