Investigating gamma-ray emission of the Cygnus cocoon with 12 years of Fermi-LAT data

Massive star-forming regions are genuine reservoirs of energy and potential sources of non-thermal particles, but their role in Galactic cosmic-ray acceleration and propagation is still poorlyunderstood. Gamma-ray observations of the Cygnus X star-forming region revealed the presenceof a cocoon of freshly-accelerated cosmic rays, making it one of the best examples to investigatethese issues. However, the exact acceleration sites and mechanisms, the nature of the particles, andhow they propagate through the cocoon have not been firmly established yet, and the contributionfrom other gamma-ray sources in this crowded region remains uncertain. We present a newin-depth analysis of more than 12 years of observations from the Fermi Large Area Telescopecombined with high-resolution interstellar medium tracer data to improve the understanding ofgamma-ray emission from the Cygnus region. The evolution of the cocoon morphology as afunction of energy and its spectrum up to 1TeV will be used to shed new light on the openquestions about the physical processes shaping the young cosmic-ray population in Cygnus X.