Simulating the interstellar medium and stellar feedback on a moving mesh: implementation and isolated galaxies

Abstract

We introduce the Stars and MUltiphase Gas in GaLaxiEs -SMUGGLE model, an explicit and comprehensive stellar feedback model for the moving-mesh code AREPO. This novel sub-resolution model resolves the multiphase gas structure of the interstellar medium and self-consistently generates gaseous outflows. The model implements crucial aspects of stellar feedback including photoionization, radiation pressure, energy and momentum injection from stellar winds and from supernovae. We explore this model in high-resolution isolated simulations of Milky Way-like disc galaxies. Stellar feedback regulates star formation to the observed level and naturally captures the establishment of a Kennicutt-Schmidt relation. This result is achieved independent of the numerical mass and spatial resolution of the simulations. Gaseous outflows are generated with average mass loading factors of the order of unity. Strong outflow activity is correlated with peaks in the star formation history of the galaxy with evidence that most of the ejected gas eventually rains down onto the disc in a galactic fountain flow that sustains late-time star formation. Finally, the interstellar gas in the galaxy shows a distinct multiphase distribution with a coexistence of cold, warm and hot phases.

Simulating the interstellar medium of galaxies with radiative transfer, non-equilibrium thermochemistry, and dust

“…The star formation efficiency is a free parameter which is set to = 0.01, in line with recent observational estimates (Krumholz & Tan 2007). Additionally, following the SMUGGLE implementation, we impose the condition that the star forming gas cloud needs to be self-gravitating in order to form stars (Equation 9; Marinacci et al 2019). Although we do follow the formation of molecular hydrogen in our simulations, we choose not to tie the star formation rate to the abundance of H 2, with the goal of recovering the molecular Kennicutt-Schmidt (Bigiel et al 2008;Leroy et al 2008) relation naturally in our simulations without the need to impose it.…”

“…In recent years, increases in computational power have made it possible to simulate galaxy formation in a more resolved manner. These models have prescriptions for low temperature gas cooling, supernova (SN) energy and momentum input based on high resolution simulations of SN explosions (e.g., Thornton et al 1998;Kim & Ostriker 2015;Martizzi et al 2015) and a stochastic model for photoheating and radiation pressure feedback (Hopkins et al 2014(Hopkins et al , 2018bSmith et al 2018;Marinacci et al 2019). The resulting simulations partially resolve giant molecular clouds, which are the sites for star formation, produce a multiphase interstellar medium (ISM) in a self-consistent manner, and reproduce resolved properties of galaxies such as local group dwarfs (Wetzel et al 2016;Smith et al 2019), globular cluster formation (Ma et al 2019), and disc morphology and kinematics (Ma et al 2017).…”

“…Radiation pressure, both by UV and trapped IR radiation can impart momentum into the ISM, which helps drive large scale galactic winds (Murray et al 2011). While some sub-resolution models for the effect of radiation exists (Hopkins et al 2014;Hu et al 2017;Hopkins et al 2018b;Marinacci et al 2019), it is unclear if they accurately capture this process in a wide variety of environments (Rosdahl & Teyssier 2015;Kannan et al 2018;Fujimoto et al 2019).…”

“…While these processes have been studied individually in galaxies (e.g., Glover & Mac Low 2007;Gnedin & Kravtsov 2011;Christensen et al 2012;Asano et al 2013;Rosdahl & Teyssier 2015;McKinnon et al 2016;Richings & Schaye 2016;McKinnon et al 2017;Hopkins et al 2018a;McKinnon et al 2018;Agertz et al 2019;Nickerson et al 2019), their combined impact has still not been modeled properly. This paper combines a state-of-the-art radiation hydrodynamics module with a non-equilibrium thermochemistry module that accounts for H 2 coupled to realistic dust formation and destruction, all integrated into a novel stellar feedback framework, the Stars and Multiphase Gas in Galaxies (SMUG-GLE) model (Marinacci et al 2019). We test this model on isolated MW simulation at different resolutions and radiation field properties.…”

Inconsistencies arising from the coupling of galaxy formation sub-grid models to pressure-smoothed particle hydrodynamics

“…Cosmological simulations typically include so-called sub-grid physics that aims to represent underlying physics that is below the (mass) resolution limit (which is usually around 10 3−7 M ; Schaye 2010; Vogelsberger et al 2014;Schaye et al 2015;Hopkins et al 2018;Davé et al 2019;Marinacci et al 2019). This is commonplace in many fields, and is essential in galaxy formation to reproduce many of the observed properties of galaxies.…”