Simulations of Galactic Outflows Driven by Active Galactic Nuclei and Starbursts

Abstract

Using the hydro code Athena++, we run a series of large-scale hydrodynamic simulations of galactic outflows on a scale of ∼5 kpc scale over a time period of 5 Myr. We compare the kinematics, composition, and simulated X-ray emission of starburst (SB) versus active galactic nuclei (AGN) dominated galactic outflows. Our set of simulations includes galactic outflows driven solely by a nuclear SB, an AGN wind, and a mixture of SBs and AGN winds. We find significant differences in the kinematics, composition, and simulated X-ray emission between SB- versus AGN-dominated outflows. Starburst-driven outflows are characterized by turbulent, multiphase, complex flows, with each phase having a distinct kinematic profile (as traced by various oxygen ions), while AGN-driven outflows are more symmetric, more single phase, with primarily very hot (>107 K) gas, and are smooth in appearance. In mixed SB-AGN simulations, the dominant component (SB or AGN) determines the outflow characteristics. In cases where the energy input of the SB is similar to the energy of the AGN, the resulting outflow appears similar to the SB-only outflow, but when the energy input from the AGN wind is much greater than the SB then the outflow appears similar to the AGN-only outflow. When we generate synthetic X-ray observations, the AGN-dominated outflows are essentially invisible in soft to medium-energy X-rays (0.1–10.0 keV), but the SB-driven outflows show complex filamentary structures that are visible in the X-ray. Finally, we show the observational possibilities for various proposed and future X-ray telescopes.