Synthetic CO, H2 and HI surveys of the Galactic 2nd Quadrant, and the properties of molecular gas

TL;DR

This study uses simulations with feedback and self-gravity to generate synthetic CO, H2, and HI observations of the Milky Way's 2nd Quadrant, comparing them to real data to evaluate model accuracy.

Contribution

It demonstrates that including feedback and self-gravity in galaxy simulations is essential for accurately reproducing observed molecular gas properties.

Findings

Models with feedback and self-gravity match observed CO and H2 distributions.

Chemistry and feedback variations have limited impact on statistical properties.

All models underproduce molecular gas compared to observations.

Abstract

We present CO, H2, HI and HISA distributions from a set of simulations of grand design spirals including stellar feedback, self-gravity, heating and cooling. We replicate the emission of the 2nd Galactic Quadrant by placing the observer inside the modelled galaxies and post process the simulations using a radiative transfer code, so as to create synthetic observations. We compare the synthetic datacubes to observations of the 2nd Quadrant of the Milky Way to test the ability of the current models to reproduce the basic chemistry of the Galactic ISM, as well as to test how sensitive such galaxy models are to different recipes of chemistry and/or feedback. We find that models which include feedback and self-gravity can reproduce the production of CO with respect to H2 as observed in our Galaxy, as well as the distribution of the material perpendicular to the Galactic plane. While changes in the chemistry/feedback recipes do not have a huge impact on the statistical properties of the chemistry in the simulated galaxies, we find that the inclusion of both feedback and self-gravity are crucial ingredients, as our test without feedback failed to reproduce all of the observables. Finally, even though the transition from H2 to CO seems to be robust, we find that all models seem to underproduce molecular gas, and have a lower molecular to atomic gas fraction than is observed. Nevertheless, our fiducial model with feedback and self-gravity has shown to be robust in reproducing the statistical properties of the basic molecular gas components of the ISM in our Galaxy.