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 through hydrodynamic simulations. Employing a sink-particle module, we self-consistently resolve the star formation and feedback processes, avoiding the reliance on various assumed models. We probe the effects of different stellar feedback mechanisms, gas return from star-forming clouds and gas disc mass on the starburst and outflow. Our simulations can generate a starburst that lasts $\sim25$ Myr, peaking at 20-50 $\rm{M_{\odot} yr<sup>{-1}}$. However, the total stellar mass formed in the starburst often exceeds M82's estimated value. The outflow's launch occurs in two stages. Initially, continuous SNe explosions form small bubbles, merging into a super bubble foam composed of warm/hot gas and high-density cool filaments. After $\sim10$ Myr of SN injection, the super bubble breakout the disc, marking the second stage, which takes $\sim15$ Myr to develop a kpc-scale outflow. Our simulations reveal that cool filaments within the ISM can survive from the stellar feedback, then were entrained into the outflow and stretched to hundreds pc in length. While the mass loading factor of the well-developed outflow is comparable to M82, the cool gas mass outflow rate is often lower, and its velocity is slower than the estimated value in M82 by $\sim60\%$. Warm and hot gas are $\sim25\%$ slower. SN feedback acts as the primary driver of the outflow, while gas return significantly influences the starburst and outflow. Other factors have moderate effects. To address the shortcoming in our results, enhanced SN feedback effect due to clustered SNe is likely necessary.