http://arxiv.org/abs/1608.03930
Fast radio bursts (FRBs) have been identified as extragalactic sources which can make a probe of turbulence in the intergalactic medium (IGM) and their host galaxies. To account for the observed millisecond pulses caused by scatter broadening, we examine a variety of possible models of electron density fluctuations in both the IGM and the host galaxy medium. We find that a shallow power-law spectrum of density, which may arise in highly supersonic turbulence with pronounced local dense structures of shock-compressed gas in the host interstellar medium (ISM), can produce the required density enhancements at sufficiently small scales to interpret the scattering timescale of FRBs. It implies that an FRB residing in a galaxy with efficient star formation in action tends to have a broadened pulse. The scaling of the scattering time with dispersion measure (DM) in the host galaxy varies in different turbulence and scattering regimes. The host galaxy can be the major origin of scatter broadening, but contribute to a small fraction of the total DM. We also find that the sheet-like structure of density in the host ISM associated with folded magnetic fields cannot give rise to strong scattering. Furthermore, valuable insights into the IGM turbulence concerning the detailed spatial structure of density and magnetic field can be gained from the observed scattering timescale of FRBs. Our results are in favor of the suppression of micro-plasma instabilities and the validity of collisional-magnetohydrodynamic (MHD) description of turbulence properties in the collisionless IGM.
S. Xu and B. Zhang
Tue, 16 Aug 16
18/57
Comments: 14 pages, resubmitted after addressing the referee’s comments
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