A Spatial Gap in the Sky Distribution of Fast Radio Burst Detections Coinciding with Galactic Plasma Overdensities

Abstract

We analyze the positional and morphological properties of about 3600 unique fast radio burst (FRB) sources reported in the second FRB catalog generated by the Canadian Hydrogen Intensity Mapping Experiment (CHIME) telescope. We find a two-dimensional dependence of FRB detections on sky position, and identify a significant absence of detections in a roughly circular region centered at Galactic coordinates (77.7${}^{\circ }$, 0.9${}^{\circ }$), spanning an area of 213.6 deg${}^2$. This detection gap spatially coincides with the Cygnus X region $--$ a plasma-rich star-forming region in the Milky Way. This feature is most likely the result of increased sky temperature and strong multi-path scattering by turbulent ionized plasma, which broadens the FRB signals beyond detectability in the CHIME band. Our simulations yield a mean of 6 expected FRB detections within the gap when accounting for the elevated sky temperature in the direction of the detection gap. We infer that a lower limit of the maximum scattering timescale ${\tau }_{\mathrm{sc},1\mathrm{GHz}}\ge 5.59$ ms, obtained without assuming a model of the Galactic electron distribution, is sufficient to suppress the brightness of all coincident FRBs. A similar suppression is seen in Catalog 2 along other high-emission measure (EM) sightlines (i.e., EM$\ge$2900 pc cm${}^{-6}$), further supporting a broader trend of suppression due to Galactic scattering. Future very long baseline interferometry (VLBI) measurements of scattering disks with CHIME Outriggers could help confirm our interpretation. Our work highlights the notion that FRBs can serve as new, model-independent tracers of the warm ionized medium within our Milky Way Galaxy.

arXiv comment21 pages, 9 figures. Accepted for Publication in ApJL

References in corpus (49)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• The ATNF Pulsar Catalogue
• A bright millisecond radio burst of extragalactic origin
• A New Electron Density Model for Estimation of Pulsar and FRB Distances
• A Population of Fast Radio Bursts at Cosmological Distances
• Giant Gamma-ray Bubbles from Fermi-LAT: AGN Activity or Bipolar Galactic Wind?
• A fast radio burst associated with a Galactic magnetar
• A bright millisecond-duration radio burst from a Galactic magnetar
• Fast Radio Bursts
• Fast Radio Bursts: An Extragalactic Enigma
• The First CHIME/FRB Fast Radio Burst Catalog
• A Living Theory Catalogue for Fast Radio Bursts
• CHIME/FRB Detection of Eight New Repeating Fast Radio Burst Sources
• The WISE Catalog of Galactic HII Regions
• The CHIME Fast Radio Burst Project: System Overview
• Multifrequency Observations of Radio Pulse Broadening and Constraints on Interstellar Electron Density Microstructure
• Parallaxes and proper motions of interstellar masers toward the Cygnus X star-forming complex. I. Membership of the Cygnus X region
• Searches for Fast Radio Transients
• The Electron Temperature Gradient in the Galactic Disk
• Interpretation of parabolic arcs in pulsar secondary spectra
• LRP 2020 Whitepaper: The Canadian Hydrogen Observatory and Radio-transient Detector (CHORD)
• FAST observations of an extremely active episode of FRB 20201124A: I. Burst morphology
• The CHIME Pulsar Project: System Overview
• Blinkverse: A Database of Fast Radio Bursts
• An analysis pipeline for CHIME/FRB full-array baseband data
• An FRB Sent Me a DM: Constraining the Electron Column of the Milky Way Halo with Fast Radio Burst Dispersion Measures from CHIME/FRB
• A Large Scale Magneto-ionic Fluctuation in the Local Environment of Periodic Fast Radio Burst Source, FRB 20180916B
• PALFA Single-Pulse Pipeline: New Pulsars, Rotating Radio Transients and a Candidate Fast Radio Burst
• Revealing the Dynamic Magneto-ionic Environments of Repeating Fast Radio Burst Sources through Multi-year Polarimetric Monitoring with CHIME/FRB
• The FAST Galactic Plane Pulsar Snapshot survey: VI. The discovery of 473 new pulsars
• Modelling annual scintillation arc variations in PSR J1643-1224 using the Large European Array for Pulsars
• Disentangling the spatial substructure of Cygnus OB2 from Gaia DR2
• Synthesizing the repeating FRB population using frbpoppy
• The Analytical Solution to the Temporal Broadening of a Gaussian-Shaped Radio Pulse by Multipath Scattering from a Thin Screen in the Interstellar Medium
• No Evidence for Galactic Latitude Dependence of the Fast Radio Burst Sky Distribution
• An Injection System for the CHIME/FRB Experiment
• Radio Scattering Horizons for Galactic and Extragalactic Transients
• Ionization Profiles of Galactic HII Regions
• Filamentary structures of ionized gas in Cygnus X
• Discovery of High-Velocity H$\alpha$ Emission in the Direction of the Fermi Bubble
• The historical record of massive star formation in Cygnus
• The presence of interstellar scintillation in the 15 GHz interday variability of 1158 OVRO-monitored blazars
• A census of compact sources at 162MHz: first data release from the MWA Phase II IPS Survey
• The FAST Galactic Plane Pulsar Snapshot survey: IV. Discovery of five fast radio bursts
• Hubble constant constraint using 117 FRBs with a more accurate probability density function for ${\mathrm{DM}}_{\mathrm{diff}}$
• Multi-frequency VLBA Observations of the Compact Double B2 2050+36: Constraints on Interstellar Scattering Revisited
• High frequency VLBI observations of the scatter broadened quasar B2005+403
• A pulsar-like swing in the polarisation position angle of a nearby fast radio burst
• A multi-wavelength study of Galactic H II regions with extended emission

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