Pulsar scattering as a probe for structures in the interstellar medium

TL;DR

This study uses pulsar scattering data to identify and model structures within the interstellar medium, revealing known and new features like a superbubble, and demonstrating the potential of scattering measurements as an ISM exploration tool.

Contribution

The paper develops a method to connect pulsar scattering data with ISM structures, including the discovery of a new superbubble, enhancing understanding of Galactic ISM complexity.

Findings

Identified ISM structures associated with Vela supernova remnant and a new superbubble G38.

Constructed a smooth model of Galactic pulsar scattering distribution.

Showed that small-scale structures dominate scattering correlation.

Abstract

Due to the inhomogeneity of electron number density, radio waves emitted by pulsars undergo scattering as they pass through the interstellar medium (ISM). However, a connection between large-scale pulsar scattering data and the structure of the Galactic ISM has yet to be established. In this paper, we explore the capability of pulsar scattering time data in discovering structures in the ISM. Using a large dataset of scattering time measurements for 473 pulsars, we fit the pulsar reduced scattering intensity as a function of Galactic latitude and distance, constructing a smooth model of the Galactic pulsar scattering distribution. By comparing this smooth distribution with observational data, we identify two ISM structures responsible for pulsar scattering, one is associated with the Vela supernova remnant region within the Gum Nebula, while the other is a newly discovered structure -- a distant superbubble, G38, located at a distance of 2.3 kpc with a size of ~50 pc. Analysis of the correlation coefficient of the pulsar scattering distribution shows that the correlation is dominated by structures smaller than 0.15 kpc -- the closest separation approachable by the current dataset. As measurements of the pulsar scattering time continue to increase in the future, they can potentially become an independent tool for exploring structures in the ISM.