Past activity of Sgr A* is unlikely to affect the local cosmic-ray spectrum up to the TeV regime

Abstract

The presence of kiloparsec-sized bubble structures in both sides of the Galactic plan suggests active phases of Sgr A${}^{\star }$, the central supermassive black hole of the Milky-Way in the last 1-6 Myr. The contribution of such event on the cosmic-ray flux measured in the solar neighborhood is investigated with numerical simulations. We evaluate whether the population of high-energy charged particles emitted by the Galactic Center could be sufficient to significantly impact the CR flux measured in the solar neighborhood. We present a set of 3D magnetohydrodynamical simulations, following the anisotropic propagation of CR in a Milky - Way like Galaxy. Independent populations of cosmic-ray are followed through time, originating from two different sources types, namely Supernovae and the Galactic Center. To assess the evolution of the CR flux spectrum properties, we split these populations into two independent energy groups of 100 GeV and 10 TeV. We find that the anisotropic nature of cosmic-ray diffusion dramatically affects the amount of cosmic-ray energy received in the solar neighborhood. Typical timescale to observe measurable changes in the CR spectrum slope is of the order 10 Myr, largely surpassing estimated ages of the Fermi bubbles in the AGN jet-driven scenario. We conclude that a cosmic-ray outburst from the Galactic center in the last few Myr is unlikely to produce any observable feature in the local CR spectrum in the TeV regime within times consistent with current estimates of the Fermi bubbles ages.

arXiv comment9 pages, 10 figures, Accepted for publication in Astronomy & Astrophysics

References in corpus (22)

• Cosmic-ray propagation and interactions in the Galaxy
• Giant Gamma-ray Bubbles from Fermi-LAT: AGN Activity or Bipolar Galactic Wind?
• A High Order Godunov Scheme with Constrained Transport and Adaptive Mesh Refinement for Astrophysical MHD
• The Spectrum and Morphology of the Fermi Bubbles
• The Large-scale Bipolar Wind in the Galactic Center
• The Fermi Bubbles. I. Possible Evidence for Recent AGN Jet Activity in the Galaxy
• A sub-parsec resolution simulation of the Milky Way: Global structure of the ISM and properties of molecular clouds
• Preserving Monotonicity in Anisotropic Diffusion
• Diffusive propagation of cosmic rays from supernova remnants in the Galaxy. I: spectrum and chemical composition
• The Fermi Bubbles: Supersonic AGN Jets with Anisotropic Cosmic Ray Diffusion
• AGN Flickering and Chaotic Accretion
• Bipolar-Hyper-Shell Galactic Center Statrburst Model: Further Evidence from ROSAT Data and New Radio and X-ray Simulations
• Transition from galactic to extragalactic cosmic rays
• The Interaction of the Fermi Bubbles with the Milky Way's Hot Gas Halo
• Fermi and eRosita bubbles as relics of the past activity of the Galactic black hole
• A fast, robust, and simple implicit method for adaptive time-stepping on adaptive mesh-refinement grids
• Gamma Rays from Cosmic Rays in Supernova Remnants
• An implicit scheme for solving the anisotropic diffusion of heat and cosmic rays in the RAMSES code
• Cosmic ray spectrum in the local Galaxy
• Simulating the Fermi Bubbles as Forward Shocks Driven by AGN Jets
• Shock-accelerated cosmic rays and streaming instability in the adaptive mesh refinement code Ramses
• Contribution of the Galactic center to the local cosmic-ray flux