Refractive lensing of scintillating FRBs by sub-parsec cloudlets in the multi-phase CGM

Abstract

We consider the refractive lensing effects of ionized cool ($T\sim 10^4\mathrm{K}$) gas cloudlets in the circumgalactic medium (CGM) of galaxies. In particular, we discuss the combined effects of lensing from these cloudlets and scintillation from plasma screens in the Milky Way interstellar medium (ISM). We show that, if the CGM comprises a mist of sub-parsec cloudlets with column densities of order $10^{17}{\mathrm{cm}}^{-2}$ (as predicted by McCourt et al. 2018), then FRBs whose sightlines pass within a virial radius of a CGM halo will may be lensed into tens of refractive images with a $\sim 10\mathrm{ms}$ scattering timescale. When these images are formed, they will be resolved by scintillating screens in the Milky Way ISM, and will suppress the observed scintillation. We illustrate this effect in refractive lensing and argue that positive detections of FRB scintillation may constrain the properties of these cool-gas cloudlets, with current scintillation observation weakly disfavouring the cloudlet model. We propose that sheet-like geometries for the cool gas in the CGM can reconcile quasar absorption measurements (from which we infer the presence of the cool gas with structure on sub-parsec scales) and the unexpected lack of lensing signals from this gas thus far observed.

References in corpus (25)

• A repeating fast radio burst source localised to a nearby spiral galaxy
• Dense magnetized plasma associated with a fast radio burst
• A cosmic web filament revealed in Lyman-alpha emission around a luminous high-redshift quasar
• FRB 121102 Bursts Show Complex Time-Frequency Structure
• Characterizing the Circumgalactic Medium of Nearby Galaxies with HST/COS and HST/STIS Absorption-Line Spectroscopy
• A Characteristic Scale for Cold Gas
• Quasar Quartet Embedded in Giant Nebula Reveals Rare Massive Structure in Distant Universe
• Faint Scattering Around Pulsars: Probing the Interstellar Medium on Solar System Size Scales
• 100 Microarcsecond Resolution VLBI Imaging of Anisotropic Interstellar Scattering towards Pulsar B0834+06
• Interpretation of parabolic arcs in pulsar secondary spectra
• The Gaussian Plasma Lens in Astrophysics. Refraction
• Quasars Probing Quasars III: New Clues to Feedback, Quenching, and the Physics of Massive Galaxy Formation
• Pulsar scintillations from corrugated reconnection sheets in the ISM
• Quasars Probing Quasars VIII. The Physical Properties of the Cool Circumgalactic Medium Surrounding z ~ 2-3 Massive Galaxies Hosting Quasars
• The Large Dispersion and Scattering of FRB 20190520B are Dominated by the Host Galaxy
• Refractive Convergent Plasma Lenses explain ESE and pulsar scintillation
• Redshift Estimation and Constraints on Intergalactic and Interstellar Media from Dispersion and Scattering of Fast Radio Bursts
• Predicting Pulsar Scintillation from Refractive Plasma Sheets
• A Scintillation Arc Survey of 22 Pulsars with Low to Moderate Dispersion Measures
• Radio wave scattering by circumgalactic cool gas clumps
• Regimes in astrophysical lensing: refractive optics, diffractive optics, and the Fresnel scale
• Constraining the Vela Pulsar's Radio Emission Region Using Nyquist-Limited Scintillation Statistics
• Resolving the Emission Regions of the Crab Pulsar's Giant Pulses II. Evidence for Relativistic Motion
• Imaginary images and Stokes phenomena in the weak plasma lensing of coherent sources
• Modelling Annual Scintillation Velocity Variations of FRB 20201124A

Cited by in corpus (4)

• CGM cloud sizes from refractive FRB scattering
• Microphysics of Circumgalactic Turbulence Probed by Fast Radio Bursts and Quasars
• Redshift Distributions of Fast Radio Bursts Inferred Using Clustering in Dispersion Measure Space
• Scintillometry of Fast Radio Bursts: Resolution effects in two-screen models