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

Yuval Birnboim*, Shmuel Balberg, Romain Teyssier

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

14 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 languageAmerican English
Pages (from-to)3678-3692
Number of pages15
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
StatePublished - 11 Mar 2015

Bibliographical note

Publisher Copyright:
© 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.


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


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