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

Galactic winds from starbursts and Active Galactic Nuclei (AGN) are thought to play an important role in driving galaxies along the starburst-AGN sequence. Here, we assess the impact of these winds on the CO emission from galaxy mergers, and, in particular, search for signatures of starburst and AGN-feedback driven 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 ∼108-109 M⊙ 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 starburstdriven 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, regardless of the associated wind model. In models with winds, however, 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. Subject headings: galaxies: active, starburst, ISM – quasars: general – line: profiles – ISM: jets and outflows