A new method of reconstructing Galactic three-dimensional structures using ultralong-wavelength radio observations

TL;DR

This paper proposes a method to reconstruct the three-dimensional distribution of Galactic electrons using ultralong-wavelength radio observations, which will be enabled by upcoming space missions and can reveal key astrophysical processes.

Contribution

It introduces a novel approach to reconstruct the 3D Galactic electron distribution from multi-frequency ultralong-wavelength radio maps, a new application for upcoming space experiments.

Findings

Demonstrates the reconstruction method using NE2001 model as input

Shows the potential of ultralong-wavelength observations for Galactic studies

Provides a visual animation of the reconstructed electron distribution

Abstract

The free-free absorption of low frequency radio waves by thermal electrons in the warm ionized medium of our Galaxy becomes very significant at $\lesssim 10$ MHz (ultralong-wavelength), and the absorption strength depends on the radio frequency. Upcoming space experiments such as the Discovering Sky at the Longest wavelength (DSL) and Farside Array for Radio Science Investigations of the Dark ages and Exoplanets (FARSIDE) will produce high-resolution multi-frequency sky maps at the ultralong-wavelength, providing a new window to observe the Universe. In this paper we propose that from these ultralong-wavelength multi-frequency maps, the three-dimensional distribution of the Galactic electrons can be reconstructed. This novel and robust reconstruction of the Galactic electron distribution will be a key science case of those space missions. Ultralong-wavelength observations will be a powerful tool for studying the astrophysics relevant to the Galactic electron distribution, for example, the impacts of supernova explosions on electron distribution, and the interaction between interstellar atoms and ionizing photons escaped from the HII regions around massive stars. An animation shows the reconstructed results using {\tt NE2001} model as input test. On ArXiv, it is given in the directory: Ancillary files. In the paper the animation is linked to Fig. 5.