Probing the Cosmic Web with Fast Radio Bursts: II. Scintillation

To be submitted this week. Scintillation of FRB signals as probes of multiphase gas in cosmic web sheets, filaments, and the CGM.

Sharon Lapiner, Nir Mandelker, Paz Beniamini, S. Peng Oh

Fraction of FRBs whose MW scintillation is suppressed by halo masses of $M_{\rm h}\geq10^{12}{\,\rm M_{\odot}}$ haloes ($f_{\rm FRBs, MW}$, y-axis). To allow comparison with future non-localized samples, we express $f_{\rm FRBs, MW}$ as a function of the average extragalactic dispersion measure (DM), ${\rm DM_{IGM}}$ (bottom x-axis). The top x-axis represents the redshift of the source. We assume a sightline passes through a halo with an impact parameter of $b=0.7$, and through a MW screen with a typical scintillation bandwidth $\delta\nu_{\rm MW}(\nu=1{\rm GHz})=1 {\,\rm MHz}$, and a distance from the observer of $d_{\rm MW}=1{\,\rm kpc}$. The different colors represent the observed frequency, and the line styles indicate the volume-filling fraction ($f_{\rm v}$) of the cold cloudlets in haloes. For instance, $\gtrsim 40\%$ of the FRBs with excess DM of $\gtrsim 500 {\,\rm pc\, cm^{-3}}$ are expected to be suppressed below a frequency of $\nu\sim 1.4{\,\rm GHz}$ by haloes with $f_{\rm v}\gtrsim 10^{-4}$. We explore several possibilities of deviations from the fiducial model in the paper, yielding testable predictions to be compared with forthcoming surveys.