The Galactic gamma-ray club

TL;DR

The paper discusses recent developments in gamma-ray sources within the Milky Way, highlighting new detections, ongoing debates about emission origins, and the importance of magnetic field measurements for understanding particle acceleration.

Contribution

It provides a comprehensive overview of newly identified gamma-ray sources and emphasizes the need for magnetic field data to better understand acceleration mechanisms.

Findings

Recent gamma-ray sources include supernova remnants, pulsar wind nebulae, and binary systems.

Detection of both jet and pulsar-wind emissions in binaries.

Upcoming observations will enable statistical analysis of different accelerators.

Abstract

The exclusive Galactic gamma-ray club has opened up to new members. Supernova remnants, pulsar wind nebulae, and massive binary systems hosting a compact object have recently joined the young pulsars as firmly established sources of gamma rays in the Milky Way. Massive young stellar clusters are on the waiting list to join the club. Only the fine imaging recently obtained at TeV energies could resolve specific sources. The samples are sparse, but raise exciting questions. The jet or pulsar-wind origin of the emission in binaries has been hotly debated, but it seems that both types of systems have been recently detected. The nature of the radiation in shock accelerators is still questioned: do nuclei contribute a lot, a little, or not to the gamma rays and what energy do they carry away from the shock budget? The acceleration process and the structural evolution of the pulsar winds are still uncertain. The magnetic field distribution in all these systems is a key, but poorly constrained, ingredient to model the multi-wavelength data, particle transport and electron ageing. It must, however, be determined in order to efficiently probe particle distributions and the acceleration mechanisms. The source samples soon to be expected from GLAST and the Cherenkov telescopes should bring new valuable test cases and they will, for the first time, shed statistical light on the collective behaviour of these different types of accelerators.