Revisiting the galactic winds in M82 I: the recent starburst and launch of outflow in simulations

ABSTRACT We revisit the launch of the galactic outflow in M82 using hydrodynamic simulations. Employing a sink-particle module, we self-consistently resolve star formation and feedback, avoiding reliance on simplified models. We investigate the effects of stellar feedback mechanisms, gas return from star-forming clouds, and disc mass on the starburst and outflow. Our simulations generate a starburst lasting $\sim 25$ Myr, peaking at 20–50 $\rm {{\rm M}_{\odot }\,yr^{-1}}$, although the total stellar mass often exceeds M82’s estimated value. The outflow develops in two stages: initially, continuous SNe form small bubbles that merge into a superbubble containing warm/hot gas and intermediate- to high-density cool filaments. After $\sim 10$ Myr, the superbubble breaks out of the disc, and within $\sim 15$ Myr a kpc-scale outflow forms. Cool filaments survive stellar feedback, become entrained in the wind, and stretch to hundreds of parsecs. Transport from the cool interstellar medium is the dominant net contributor to the total mass of the cool phase in the outflow, whereas transfers from hotter phases, such as through condensation or precipitation, provide only a minor net contribution, likely offset by simultaneous transfer from the cool phase back to hotter phases. While the mass-loading factor is comparable to M82, the cool gas outflow rate and velocity are lower, with velocities $\sim 60~{{\ \rm per\ cent}}$ below observed values; warm and hot gas are $\sim 25~{{\ \rm per\ cent}}$ slower. SN feedback is the primary driver, and gas return significantly influences the starburst and outflow, while other factors are secondary. Stronger clustered SN feedback is likely required to better match observations.