Nonthermal X-rays from low-energy cosmic rays in the arches cluster region

Abstract

We have studied in detail the production of nonthermal line and continuum X-rays by interaction of accelerated electrons and ions with a neutral ambient gas, and have applied the resulting models to XMM-Newton observations of the X-ray emission emanating from the Arches cluster region near the Galactic center. The diffuse X-ray emission prominent in the 6.4 keV Fe K˛ line surrounding the very massive cluster is likely excited by low-energy cosmic ray ions produced in the ongoing supersonic collision between the star cluster and an adjacent molecular cloud. The nonthermal emission from this region probably offers at present the best available signature for a source of low-energy hadronic cosmic rays in the Galaxy.