MHD decomposition explains diffuse $\gamma$-ray emission in Cygnus X

Abstract

Cosmic-ray (CR) diffusion is the result of the interaction of such charged particles against magnetic fluctuations. These fluctuations originate from large-scale turbulence cascading towards smaller spatial scales, decomposed into three different modes, as described by $magneto-hydro-dynamics$ (MHD) theory. As a consequence, the description of particle diffusion strongly depends on the model describing the injected turbulence. Moreover, the amount of energy assigned to each of the three modes is in general not equally divided, which implies that diffusion properties might be different from one region to another. Here, motivated by the detection of different MHD modes inside the Cygnus-X star-forming region, we study the 3D transport of CRs injected by two prominent sources within a two-zone model that represents the distribution of the modes. Then, by convolving the propagated CR-distribution with the neutral gas, we are able to explain the $\gamma$-ray diffuse emission in the region, observed by the Fermi-LAT and HAWC Collaborations. Such a result represents an important step in the long-standing problem of connecting the CR observables with the micro-physics of particle transport.

arXiv comment7 pages, 4 figures

References in corpus (17)

• The Milky Way in Molecular Clouds: A New Complete CO Survey
• Scattering of Cosmic Rays by Magnetohydrodynamic Interstellar Turbulence
• Cosmic Ray Scattering and Streaming in Compressible Magnetohydrodynamic Turbulence
• Cosmic Ray Propagation: Nonlinear Diffusion Parallel and Perpendicular to Mean Magnetic Field
• First Detection of sub-PeV Diffuse Gamma Rays from the Galactic Disk: Evidence for Ubiquitous Galactic Cosmic Rays beyond PeV Energies
• The origin of Galactic cosmic rays: challenges to the standard paradigm
• Diffusive propagation of cosmic rays from supernova remnants in the Galaxy. II: anisotropy
• Particle acceleration in winds of star clusters
• Discovery of extended VHE γ-ray emission from the vicinity of the young massive stellar cluster Westerlund 1
• HAWC observations of the acceleration of very-high-energy cosmic rays in the Cygnus Cocoon
• High-energy particles and radiation in star-forming regions
• Diffuse gamma-ray emission in the vicinity of young star cluster Westerlund 2
• Discovery of TeV Gamma-ray Emission Toward Supernova Remnant SNR G78.2+2.1
• Properties of magnetohydrodynamic modes in compressively driven plasma turbulence
• The theory of cosmic-ray scattering on pre-existing MHD modes meets data
• Identification of plasma modes in Galactic turbulence with synchrotron polarization
• SHOCKFIND - An algorithm to identify magnetohydrodynamic shock waves in turbulent clouds

Cited by in corpus (1)

• Multiple emission components in the Cygnus cocoon detected from Fermi-LAT observations