Radio Scattering Horizons for Galactic and Extragalactic Transients

Abstract Radio wave scattering can cause severe reductions in detection sensitivity for surveys of Galactic and extragalactic fast (∼ms duration) transients. While Galactic sources like pulsars undergo scattering in the Milky Way interstellar medium (ISM), extragalactic fast radio bursts (FRBs) can...

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Bibliographic Details
Published in:The Astrophysical journal 2022-07, Vol.934 (1), p.71
Main Authors: Ocker, Stella Koch, Cordes, James M., Chatterjee, Shami, Gorsuch, Miranda R.
Format: Article
Language:English
Subjects:
Astronomical models
Astrophysics
Circumgalactic medium
Electron density
Extragalactic radio sources
Galactic disk
Galactic halos
Galaxies
Halos
Intergalactic medium
Interstellar matter
Interstellar medium
Interstellar scattering
Milky Way
Pulsars
Radio bursts
Radio pulsars
Radio scattering
Radio transient sources
Radio wave scattering
Radio waves
Red shift
Sky surveys (astronomy)
Turbulence
Wave scattering
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Summary:Abstract Radio wave scattering can cause severe reductions in detection sensitivity for surveys of Galactic and extragalactic fast (∼ms duration) transients. While Galactic sources like pulsars undergo scattering in the Milky Way interstellar medium (ISM), extragalactic fast radio bursts (FRBs) can also experience scattering in their host galaxies and other galaxies intervening in their lines of sight. We assess Galactic and extragalactic scattering horizons for fast radio transients using a combination of NE2001 to model the dispersion measure and scattering time ( τ ) contributed by the Galactic disk, and independently constructed electron density models for the Galactic halo and other galaxies’ ISMs and halos that account for different galaxy morphologies, masses, densities, and strengths of turbulence. For source redshifts 0.5 ≤ z s ≤ 1, an all-sky, isotropic FRB population has simulated values of τ (1 GHz) ranging from ∼1 μ s to ∼2 ms (90% confidence, observer frame) that are dominated by host galaxies, although τ can be ≫2 ms at low Galactic latitudes. A population at z s = 5 has 0.01 ≲ τ ≲ 300 ms at 1 GHz (90% confidence), dominated by intervening galaxies. About 20% of these high-redshift FRBs are predicted to have τ > 5 ms at 1 GHz (observer frame), and ≳40% of FRBs between z s ∼ 0.5–5 have τ ≳ 1 ms for ν ≤ 800 MHz. Our scattering predictions may be conservative if scattering from circumsource environments is significant, which is possible under specific conditions. The percentage of FRBs selected against from scattering could also be substantially larger than we predict if circumgalactic turbulence causes more small-scale (≪1 au) density fluctuations than observed from nearby halos.
ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/ac75ba