The Fermi LAT view of Cygnus: a laboratory to understand cosmic-ray acceleration and transport

TL;DR

This paper uses Fermi LAT gamma-ray observations to study cosmic-ray acceleration in Cygnus X, revealing a localized CR cocoon around young stellar clusters and comparing it to the broader interstellar CR population.

Contribution

It provides the first gamma-ray evidence of a CR cocoon in Cygnus X, enhancing understanding of CR acceleration in massive star-forming regions.

Findings

Discovery of a 50-pc CR cocoon in Cygnus X

CR population in the region is similar to local interstellar space

Supports the hypothesis that star-forming regions host CR factories

Abstract

Cygnus X is a conspicuous massive-star forming region in the Local Arm of the Galaxy at ~1.4 kpc from the solar system. Gamma-ray observations can be used to trace cosmic rays (CRs) interacting with the ambient interstellar gas and low-energy radiation fields. Using the Fermi Large Area Telescope (LAT) we have discovered the presence of a 50-pc wide cocoon of freshly-accelerated CRs in the region bounded by the ionization fronts from the young stellar clusters. On the other hand, the LAT data show that the CR population averaged over the whole Cygnus complex on a scale of 400 pc is similar to that found in the interstellar space near the Sun. These results confirm the long-standing hypothesis that massive star-forming regions host CR factories and shed a new light on the early phases of CR life in such a turbulent environment.