TEMPORAL SMEARING OF TRANSIENT RADIO SOURCES BY THE INTERGALACTIC MEDIUM

Journal Article · Sun Oct 20 04:00:00 EDT 2013 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/776/2/125· OSTI ID:22270809

Macquart, Jean-Pierre

The temporal smearing of impulsive radio events at cosmological redshifts probes the properties of the ionized intergalactic medium (IGM). We relate the degree of temporal smearing and the profile of a scattered source to the evolution of a turbulent structure in the IGM as a function of redshift. We estimate the degree of scattering expected by analyzing the contributions to the scattering measure of the various components of baryonic matter embedded in the IGM, including the diffuse IGM, intervening galaxies, and intracluster gas. These estimates predict that the amount of temporal smearing expected at 300 MHz is typically as low as ∼1 ms and suggests that these bursts may be detectable with low-frequency widefield arrays. A generalization of the dispersion-measure-scattering-measure relation observed for Galactic scattering to the densities and turbulent conditions relevant to the IGM suggests that scattering measures on the order of 10{sup –6} kpc m{sup –20/3} would be expected at z ∼ 1. This scattering is sufficiently low enough that its effects would not, for most lines of sight, be manifested in existing observations of the scatter broadening in images of extragalactic compact sources. The redshift dependence on the temporal smearing discriminates between scattering that occurs in the host galaxy of the burst and the IGM, with τ{sub host}∝(1 + z){sup –3} if the scattering probes length scales below the inner scale of the turbulence or τ{sub host}∝(1 + z){sup –17/5} if the turbulence follows a Kolmogorov spectrum. This differs strongly from the expected IGM scaling τ{sub IGM} ∼ z {sup 2} for z ∼< 1 and (1 + z){sup 0.2–0.5} for z ∼> 1.

• OSTI ID: 22270809
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 776; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ASTRONOMY
ASTROPHYSICS
BARYONS
COSMIC RADIO SOURCES
COSMOLOGY
DENSITY
GALAXIES
INTERGALACTIC SPACE
MHZ RANGE
MILKY WAY
PROBES
RED SHIFT
SCATTERING
TRANSIENTS
TURBULENCE