The SILCC project – III. Regulation of star formation and outflows by stellar winds and supernovae

Abstract

We study the impact of stellar winds and supernovae on the multi-phase interstellar medium using three-dimensional hydrodynamical simulations carried out with FLASH. The selected galactic disc region has a size of (500 pc) 2 × ±5 kpc and a gas surface density of 10 M pc −2 . The simulations include an external stellar potential and gas self-gravity, radiative cooling and diffuse heating, sink particles representing star clusters, stellar winds from these clusters which combine the winds from individual massive stars by following their evolution tracks, and subsequent supernova explosions. Dust and gas (self-)shielding is followed to compute the chemical state of the gas with a chemical network. We find that stellar winds can regulate star (cluster) formation. Since the winds suppress the accretion of fresh gas soon after the cluster has formed, they lead to clusters which have lower average masses (10 2 −10 4.3 M ) and form on shorter timescales (10 −3 −10 Myr). In particular we find an anti-correlation of cluster mass and accretion time scale. Without winds the star clusters easily grow to larger masses for ∼ 5 Myr until the first supernova explodes. Overall the most massive stars provide the most wind energy input, while objects beginning their evolution as B type stars contribute most of the supernova energy input. A significant outflow from the disk (mass loading 1 at 1 kpc) can be launched by thermal gas pressure if more than 50% of the volume near the disc mid-plane can be heated to T > 3 × 10 5 K. Stellar winds alone cannot create a hot volume-filling phase. The models which are in best agreement with observed star formation rates drive either no outflows or weak outflows.

Variable interstellar radiation fields in simulated dwarf galaxies: supernovae versus photoelectric heating

“…18), as it is the over-pressurized hot gas that drives the outflows. Our result is in very good agreement with recent studies such as Walch et al (2015), Girichidis et al (2016b) or Gatto et al (2017). In addition to the effect of photoionization, we find that the adopted stellar lifetime also has an important effect on nSNII.…”

“…Including photoionization helps suppress star formation, as PE-PI-SN-cmp and noPE-PI-SNcmp both show much lower SFRs. This highlights the importance of feedback from massive stars prior to their SN events on regulating star formation in the higher gas surface density regime (see also Gatto et al (2017) who investigated the importance of stellar winds in a Milky Way setup). The fact that PE-PI-SN-cmp and noPE-PI-SN-cmp both have very similar SFR is consistent with our previous study in Paper I where we found that the SFR in dwarf galaxies is insensitive to the adopted value of G0 (constant field).…”

“…On scales below a few parsecs, the most commonly adopted sub-resolution model is the 'sink particle' approach (Bate, Bonnell & Price 1995;Li, Mac Low & Klessen 2005;Federrath et al 2010;Hubber, Walch & Whitworth 2013;Gatto et al 2017). The idea is that when a region of gas is so gravitationally unstable that it will inevitably collapse and form stars, one can simply convert it into a 'sink particle' which only interacts gravitationally but not hydrodynamically with the rest of the system.…”

“…Another important feedback mechanism we have ignored is the stellar winds from massive stars, which can play a similar role as photoionization in the sense that they both can create favorable low-density environments for the subsequent SNe to be efficient and thus promote outflows (Gatto et al 2017;Peters et al 2016). We have neglected them in this study for two reasons, one numerical and one physical.…”

Kiloparsec-scale Simulations of Star Formation in Disk Galaxies. IV. Regulation of Galactic Star Formation Rates by Stellar Feedback

“…These results illustrate the importance of considering FUV feedback in understanding the star formation activity of galactic disk systems. Similar conclusions have been reached by Peters et al (2017) in their lower (4 pc) resolution studies of a smaller (0.5 kpc by 0.5 kpc) disk patch, which builds on the previous study of a stellar wind and supernova feedback model by Gatto et al (2017).…”