THE RADIATION HYDRODYNAMICS of RELATIVISTIC SHEAR FLOWS

Eric R. Coughlin, Mitchell C. Begelman

Research output: Contribution to journalArticlepeer-review

Abstract

We present a method for analyzing the interaction between radiation and matter in regions of intense, relativistic shear that can arise in many astrophysical situations. We show that there is a simple velocity profile that should be manifested in regions of large shear that have "lost memory" of their boundary conditions, and we use this selfsimilar velocity profile to construct the surface of last scattering, or the τ ≈ 1 surface, as viewed from any comoving point within the flow. We demonstrate that a simple treatment of scattering from this τ ≈ 1 surface exactly conserves photon number, and we derive the rate at which the radiation field is heated due to the shear present in the flow. The components of the comoving radiation energy-momentum tensor are calculated, and we show that they have relatively simple, approximate forms that interpolate between the viscous (small shear) and streaming (large shear) limits. We put our expression for the energy-momentum tensor in a covariant form that does not depend on the explicit velocity profile within the fluid and, therefore, represents a natural means for analyzing general, radiation-dominated, relativistic shear flows.

Original languageEnglish (US)
Article number21
JournalAstrophysical Journal
Volume825
Issue number1
DOIs
StatePublished - Jul 1 2016
Externally publishedYes

Keywords

  • galaxies: jets
  • gamma-ray burst: general
  • radiation: dynamics
  • relativistic processes

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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