The Cosmic Ray Distribution in Sagittarius B

The HESS instrument has observed a diffuse flux of ~ TeV gamma rays from alarge solid angle around the Galactic center (GC). This emission is correlatedwith the distribution of gas in the region suggesting that the gamma raysoriginate in collisions between cosmic ray hadrons (CRHs) and ambient matter.Of particular interest, HESS has detected gamma rays from the Sagittarius (Sgr)B Molecular Cloud Complex. Prompted by the suggestion of a hadronic origin forthe gamma rays, we have examined archival 330 and 74 MHz Very Large Array radiodata and 843 MHz Sydney University Molonglo Sky Survey data covering Sgr B,looking for synchrotron emission from secondary electrons and positrons(expected to be created in the same interactions that supply the observed gammarays). Intriguingly, we have uncovered non-thermal emission, but at a levelexceeding expectation. Adding to the overall picture, recent observations bythe Atacama Pathfinder Experiment telescope show that the cosmic ray ionizationrate is ten times greater in the Sgr B2 region of Sgr B than the local value.Lastly, Sgr B2 is also a very bright X-ray source. We examine scenarios for thespectra of CRHs and/or primary electrons that would reconcile all thesedifferent data. We determine that (i) a hard (~ E^-2.2), high-energy (> TeV)population CRHs is unavoidably required by the HESS gamma ray data and (ii) theremaining broad-band, non-thermal phenomenology is explained either by a rathersteep (~ E^-2.9) spectrum of primary electrons or a (~ E^-2.7) population ofCRHs. No single, power-law population of either leptons or hadrons can explainthe totality of broadband, non-thermal Sgr B phenomenology.Comment: 45 pages, 5 figures; Minor revisions - version accepted for publication in Ap