Feedback Regulated Turbulence, Magnetic Fields, and Star Formation Rates in Galactic Disks
Abstract
We use three-dimensional magnetohydrodynamic (MHD) simulations to investigate the quasi-equilibrium states of galactic disks regulated by star formation feedback. We incorporate effects from massive-star feedback via time-varying heating rates and supernova (SN) explosions. We find that the disks in our simulations rapidly approach a quasi-steady state that satisfies vertical dynamical equilibrium. The star formation rate (SFR) surface density self-adjusts to provide the total momentum flux (pressure) in the vertical direction that matches the weight of the gas. We quantify feedback efficiency by measuring feedback yields, η c ≡ P c /ΣSFR (in suitable units), for each pressure component. The turbulent and thermal feedback yields are the same for HD and MHD simulations, ηth ~ 1 and ηturb ~ 4, consistent with the theoretical expectations. In MHD simulations, turbulent magnetic fields are rapidly generated by turbulence, and saturate at a level corresponding to ηmag,t ~ 1. The presence of magnetic fields enhances the total feedback yield and therefore reduces the SFR, since the same vertical support can be supplied at a smaller SFR. We suggest further numerical calibrations and observational tests in terms of the feedback yields.
- Publication:
-
From Interstellar Clouds to Star-Forming Galaxies: Universal Processes?
- Pub Date:
- 2016
- DOI:
- 10.1017/S1743921316007225
- arXiv:
- arXiv:1511.00018
- Bibcode:
- 2016IAUS..315...38K
- Keywords:
-
- galaxies: ISM;
- galaxies: star formation;
- galaxies: magnetic fields;
- turbulence;
- MHD;
- methods: numerical;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- To appear in Proceedings of IAU Symposium 315, From interstellar clouds to star-forming galaxies: universal processes?, P. Jablonka, P. Andre, and F.. van der Tak, eds