Speaker
Description
Measurements of cosmic particle fluxes are key to indirect dark matter detection and to modeling galactic transport of cosmic rays, but all direct measurements have been made within or near our solar system, i.e. $\sim$8 kpc from the center of the Milky Way. In this work, we constrain MeV to GeV scale electron and proton populations within the central 100 pc of the Galaxy on the basis of X-ray emission from ionizing particle interactions in the Galactic Center Molecular Cloud Sagittarius B2 (Sgr B2). X-ray emission from Sgr B2, including the characteristic Fe K$\alpha$ fluorescence line at 6.4 keV, has previously been dominated by a variable component attributed to reflection of a past outburst from the supermassive black hole Sagittarius A*. Meanwhile, any local low energy particles would also produce X-rays in Sgr B2 via ionization and excitation of the molecular gas, contributing a constant baseline flux. Since the year 2001, Fe K$\alpha$ emission from Sgr B2 has decreased by $>$ 90%, raising the possibility that it may now be dominated by particle interactions. Measurements of cosmic particle populations near the Galactic Center could help constrain models of cosmic particle transport in the Galaxy.
Keywords
Cosmic-ray protons; Cosmic-ray electrons; Galactic center; Molecular cloud; Sagittarius B2;
| Subcategory | Experimental Results |
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