On The GeV and TeV Detections of the Starburst Galaxies M82 and NGC 253 - Astrophysics > High Energy Astrophysical PhenomenaReportar como inadecuado




On The GeV and TeV Detections of the Starburst Galaxies M82 and NGC 253 - Astrophysics > High Energy Astrophysical Phenomena - Descarga este documento en PDF. Documentación en PDF para descargar gratis. Disponible también para leer online.

Abstract: The GeV and TeV emission from M82 and NGC 253 observed by Fermi, HESS, andVERITAS constrains the physics of cosmic rays CRs in these dense starbursts.We argue that the gamma rays are predominantly hadronic in origin, as expectedby previous studies. The measured fluxes imply that pionic losses are efficientfor CR protons in both galaxies: we show that a fraction F cal ~ 0.2 - 0.4 ofthe energy injected in high energy primary CR protons is lost to inelasticproton-proton collisions pion production before escape, producing gamma rays,neutrinos, and secondary electrons and positrons. We discuss the factor ~2uncertainties in this estimate, including supernova rate and leptoniccontributions to the GeV-TeV emission. We argue that gamma-ray data on ULIRGslike Arp 220 can test whether M82 and NGC 253 are truly calorimetric, and wepresent upper limits on Arp 220 from the Fermi data. We show that the observedratio of the GeV to GHz fluxes of the starbursts suggests that non-synchrotroncooling processes are important for cooling the CR electron-positronpopulation. We briefly reconsider previous predictions in light of thegamma-ray detections, including the starburst contribution to the gamma-raybackground and CR energy densities. Finally, as a guide for future studies, welist the brightest star-forming galaxies on the sky and present updatedpredictions for their gamma-ray and neutrino fluxes.



Autor: Brian C. Lacki, Todd A. Thompson, Eliot Quataert, Abraham Loeb, Eli Waxman

Fuente: https://arxiv.org/







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