The turbulent gas structure in the centers of NGC253 and the Milky Way

TL;DR

This study compares molecular gas properties in the starburst centers of NGC253 and the Milky Way, revealing that starburst activity leads to higher velocity dispersions driven by feedback processes rather than gravitational binding.

Contribution

It provides a detailed comparison of gas kinematics in starburst versus non-starburst galactic centers, highlighting the impact of feedback on gas turbulence.

Findings

NGC253 has larger line widths than the Milky Way GC.

Gas in NGC253 shows higher velocity dispersion due to feedback effects.

In the Milky Way GC, gas kinematics are consistent with gravitational binding at certain densities.

Abstract

We compare molecular gas properties in the starbursting center of NGC253 and the Milky Way Galactic Center (GC) on scales of ~1-100 pc using dendograms and resolution-, area- and noise-matched datasets in CO (1-0) and CO (3-2). We find that the size-line width relations in NGC253 and the GC have similar slope, but NGC253 has larger line widths by factors of ~2-3. The $\sigma^2/R$ dependency on column density shows that, in the GC, on scales of 10-100 pc the kinematics of gas over $N>3\times10^{21}$ cm$^{-2}$ are compatible with gravitationally bound structures. In NGC253 this is only the case for column densities $N>3\times10^{22}$ cm$^{-2}$. The increased line widths in NGC253 originate in the lower column density gas. This high-velocity dispersion, not gravitationally self-bound gas is likely in transient structures created by the combination of high average densities and feedback in the starburst. The high densities turns the gas molecular throughout the volume of the starburst, and the injection of energy and momentum by feedback significantly increases the velocity dispersion at a given spatial scale over what is observed in the GC.