Nonthermal Emission from the Arches Cluster (G0.121+0.017) and the Origin of gamma-Ray Emission from 3EG J1746-2851
NORTHWESTERN UNIV EVANSTON IL DEPT OF PHYSICS AND ASTRONOMY
Pagination or Media Count:
High-resolution Very Large Array observations of the Arches cluster near the Galactic center show evidence of continuum emission at gamma 3.6, 6, 20, and 90 cm. The continuum emission at gamma 90 cm is particularly striking because thermal sources generally become optically thick at longer wavelengths and fall off in brightness, whereas nonthermal sources increase in brightness. It is argued that the radio emission from this unique source has compact and diffuse components produced by thermal and nonthermal processes, respectively. Compact sources within the cluster arise from stellar winds of mass-losing stars, whereas diffuse emission is likely to be due to colliding wind shocks of the cluster flow that generate relativistic particles that are due to diffuse shock acceleration. We also discuss the possibility that gamma-ray emission from 3EG J1746-2851, located within 3.3 of the Arches cluster results from the inverse Compton scattering of the radiation field of the cluster.