Molecular Gas Morphological Analogues for the Milky Way

TL;DR

This paper investigates the molecular gas distribution in the Milky Way and similar galaxies, revealing common morphological features and correlations with star formation, using catalogs of molecular clouds and galaxy classifications.

Contribution

It identifies a morphological pattern linked to radial gas distribution dips in galaxies with long bars, including the Milky Way, expanding understanding of galactic structure.

Findings

Galaxies with similar patterns have long bars and radial CO dips.

Bar length correlates with the extent of the gas distribution dips.

Milky Way and similar galaxies have high stellar masses and star formation rates.

Abstract

Complete catalogs of molecular clouds in the Milky Way allow analysis of the molecular medium and the star formation properties of the Milky Way that closely follows the method used for nearby galaxies. We explore whether the big dip in the radial distribution of molecular gas in the Milky Way is peculiar and find several other galaxies with similar patterns, all with similar morphological classifications of YClxxGnR, indicating a clearly defined, long bar leading to a grand-design spiral. This category is fairly rare among galaxies in the PHANGS sample, but all galaxies with this classification have some evidence for dips in the radial distribution of CO emission. The lengths of the bars correlate with the extents of the dips. The Milky Way and the other galaxies with dips have similar stellar masses and star formation rates, both lying near the high ends of the distributions for all PHANGS galaxies.