Monday, Feb 27th: Galactic star formation rates regulated by star formation feedback

Event Date: 

Monday, February 27, 2017 - 4:00pm

Event Location: 

  • Special Physics Colloquium

Stars can form through gravitational collapse when gravity overcomes pressure support of the gaseous reservoir. On galactic scales, the gaseous interstellar medium (ISM) is mainly supported by turbulence, although thermal and magnetic supports still play moderate role. As turbulence and thermal energy dissipates rapidly in the ISM, runaway star formation would occur without efficient energy replenishment. However, observations of star-forming galaxies generally show much longer gas depletion timescales than global and local dynamical timescales. The feedback from massive stars is the most promising source of energy. In this talk, I will present numerical simulations of the multiphase ISM in galactic disks, including the most important feedback processes, FUV photoelectric heating on grains and supernova (SN) explosions. Star formation rates (SFRs) are self-regulated until total pressure support provided by feedback matches the weight of the ISM. In the magnetized ISM, turbulent magnetic fields are rapidly generated and saturate at an energy level comparable to the turbulent kinetic energy, contributing additional pressure support, and reducing SFRs about 20% compared to the unmagnetized ISM. While the relative importance of turbulence, thermal, and magnetic support varies slightly depending on the details of feedback, turbulence driven by SNe is always the most important regulator of galactic star formation. I emphasize the importance of accurately modeling feedback in order to understand not only galactic SFRs but also the realistic multiphase ISM and circumgalactic medium.