Comparing molecular gas across cosmic time-scales: the Milky Way as both a typical spiral galaxy and a high-redshift galaxy analogue

TL;DR

This paper compares molecular gas properties in the Milky Way with those in nearby and high-redshift galaxies, showing the Milky Way's Central Molecular Zone as an analogue for early universe starburst conditions.

Contribution

It demonstrates that the Milky Way's Central Molecular Zone closely resembles high-redshift galaxies, establishing the Milky Way as a comprehensive template for studying star formation across cosmic time.

Findings

Milky Way clouds are similar to those in nearby galaxies.

The Central Molecular Zone resembles high-redshift galaxies.

Low star formation rate in the CMZ suggests suppression mechanisms.

Abstract

Detailed observations of the nearest star-forming regions in the Milky Way (MW) provide the ultimate benchmark for studying star formation. The extent to which the results of these Galaxy-based studies can be extrapolated to extragalactic systems depends on the overlap of the environmental conditions probed. In this paper, we compare the properties of clouds and star-forming regions in the MW with those in nearby galaxies and in the high-redshift Universe. We find that in terms of their baryonic composition, kinematics, and densities, the clouds in the solar neighbourhood are similar to those in nearby galaxies. The clouds and regions in the Central Molecular Zone (CMZ, i.e. the inner 250 pc) of the MW are indistinguishable from high-redshift clouds and galaxies. The presently low star formation rate in the CMZ therefore implies that either (1) its gas represents the initial conditions for high-redshift starbursts or (2) some yet unidentified process consistently suppresses star formation over >100 Myr time-scales. We conclude that the MW contains large reservoirs of gas with properties directly comparable to most of the known range of star formation environments and is therefore an excellent template for studying star formation across cosmological time-scales.