The Role of Galactic Winds on Molecular Gas Emission from Galaxy Mergers

TL;DR

This study investigates how galactic winds driven by starburst activity and AGN feedback influence molecular gas emission in galaxy mergers, revealing their signatures in CO emission morphologies and line profiles.

Contribution

It combines 3D non-LTE radiative transfer with SPH simulations to demonstrate the impact of winds on CO emission and outflow signatures in merging galaxies.

Findings

Galactic winds can produce observable CO outflows of 10^8-10^9 Msun.

AGN-driven winds sustain CO outflows longer than starburst-driven winds.

Winds influence the spatial extent of CO emission in post-merger galaxies.

Abstract

We assess the impact of starburst and AGN feedback-driven winds on the CO emission from galaxy mergers, and, in particular, search for signatures of these winds in the simulated CO morphologies and emission line profiles. We do so by combining a 3D non-LTE molecular line radiative transfer code with smoothed particle hydrodynamics (SPH) simulations of galaxy mergers that include prescriptions for star formation, black hole growth, a multiphase interstellar medium (ISM), and the winds associated with star formation and black hole growth. Our main results are: (1) Galactic winds can drive outflows of masses ~10^8-10^9 Msun which may be imaged via CO emission line mapping. (2) AGN feedback-driven winds are able to drive imageable CO outflows for longer periods of time than starburst-driven winds owing to the greater amount of energy imparted to the ISM by AGN feedback compared to star formation. (3) Galactic winds can control the spatial extent of the CO emission in post-merger galaxies, and may serve as a physical motivation for the sub-kiloparsec scale CO emission radii observed in local advanced mergers. (4) Secondary emission peaks at velocities greater than the circular velocity are seen in the CO emission lines in all models. In models with winds, these high velocity peaks are seen to preferentially correspond to outflowing gas entrained in winds, which is not the case in the model without winds. The high velocity peaks seen in models without winds are typically confined to velocity offsets (from the systemic) < 1.7 times the circular velocity, whereas the models with AGN feedback-driven winds can drive high velocity peaks to ~2.5 times the circular velocity.