Galaxy evolution: Modelling the role of non-thermal pressure in the interstellar medium

Yuval Birnboim, Shmuel Balberg, Romain Teyssier

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


Galaxy evolution depends strongly on the physics of the interstellar medium (ISM). Motivated by the need to incorporate the properties of the ISM in cosmological simulations, we construct a simple method to include the contribution of non-thermal components in the calculation of pressure of interstellar gas. In our method, we treat three non-thermal components - turbulence, magnetic fields and cosmic rays - and effectively parametrize their amplitude. We assume that the three components settle into a quasi-steady-state that is governed by the star formation rate, and calibrate their magnitude and density dependence by the observed radio-FIR correlation, relating synchrotron radiation to star formation rates of galaxies. We implement our model in single-cell numerical simulation of a parcel of gas with constant pressure boundary conditions and demonstrate its effect and potential. Then, the non-thermal pressure model is incorporated into RAMSES and hydrodynamic simulations of isolated galaxies with and without the non-thermal pressure model are presented and studied. Specifically, we demonstrate that the inclusion of realistic non-thermal pressure reduces the star formation rate by an order of magnitude and increases the gas depletion time by as much. We conclude that the non-thermal pressure can prolong the star formation epoch and achieve consistency with observations without invoking artificially strong stellar feedback.

Original languageEnglish (US)
Pages (from-to)3678-3692
Number of pages15
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
StatePublished - Mar 11 2015
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • Cosmic rays
  • Galaxies: evolution
  • Hydrodynamics
  • ISM: general
  • ISM: magnetic fields


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