Inverse Compton Origin of the Hard X-Ray and Soft Gamma-Ray Emission from the Galactic Ridge

TL;DR

This paper demonstrates that the hard X-ray and soft gamma-ray emission from the Galactic ridge can be explained by inverse Compton scattering involving cosmic-ray electrons and the interstellar radiation field, providing new insights into Galactic cosmic rays.

Contribution

It presents a model using GALPROP to reproduce the Galactic ridge emission as inverse Compton scattering, incorporating a new interstellar radiation field calculation.

Findings

Emission is well explained by inverse Compton scattering.

Both primary and secondary electrons contribute.

Potential to resolve the origin of Galactic ridge emission.

Abstract

A recent re-determination of the non-thermal component of the hard X-ray to soft gamma-ray emission from the Galactic ridge, using the SPI instrument on the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) Observatory, is shown to be well reproduced as inverse-Compton emission from the interstellar medium. Both cosmic-ray primary electrons and secondary electrons and positrons contribute to the emission. The prediction uses the GALPROP model and includes a new calculation of the interstellar radiation field. This may solve a long-standing mystery of the origin of this emission, and potentially opens a new window on Galactic cosmic rays.