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arXiv · 1311.1206

Galaxy Evolution: Modeling the Role of Non-thermal Pressure in the Interstellar medium

Yuval Birnboim·Shmuel Balberg·Romain Teyssier
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Abstract

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.

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Yuval Birnboim, Shmuel Balberg, Romain Teyssier. 2015-06-08. Galaxy Evolution: Modeling the Role of Non-thermal Pressure in the Interstellar medium. https://doi.org/10.1093/mnras%2Fstu2717

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