A Cocoon of Freshly Accelerated Cosmic Rays Detected by Fermi in the Cygnus Superbubble
Abstract
The origin of Galactic cosmic rays is a century-long puzzle. Indirect evidence points to their acceleration by supernova shockwaves, but we know little of their escape from the shock and their evolution through the turbulent medium surrounding massive stars. Gamma rays can probe their spreading through the ambient gas and radiation fields. The Fermi Large Area Telescope (LAT) has observed the star-forming region of Cygnus X. The 1- to 100-gigaelectronvolt images reveal a 50-parsec-wide cocoon of freshly accelerated cosmic rays that flood the cavities carved by the stellar winds and ionization fronts from young stellar clusters. It provides an example to study the youth of cosmic rays in a superbubble environment before they merge into the older Galactic population.
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Published In
Science
Volume 334 | Issue 6059
25 November 2011
25 November 2011
Copyright
Copyright © 2011, American Association for the Advancement of Science.
Submission history
Received: 24 June 2011
Accepted: 28 October 2011
Published in print: 25 November 2011
Acknowledgments
The Fermi LAT Collaboration acknowledges support from a number of agencies and institutes for both development and the operation of the LAT as well as scientific data analysis. These include NASA and the Department of Energy in the United States; Commissariat à l’Energie Atomique et aux Énergies Alternatives, Institut de Recherche sur les Lois Fondamentales de l’Univers (CEA/IRFU) and Institut National de Physique Nucléaire et de Physique des Particules, Centre National de la Recherche Scientifique (IN2P3/CNRS) in France; Agenzia Spaziale Italiana (ASI) and Istituto Nazionale di Fisica Nucleare (INFN) in Italy; Ministry of Education, Culture, Sports, Science, and Technology (MEXT), Energy Accelerator Research Organization (KEK), and Japan Aerospace Exploration Agency (JAXA) in Japan; and the K. A. Wallenberg Foundation, Swedish Research Council, and National Space Board in Sweden. Additional support from Istituto Nazionale di Astrofisica (INAF) in Italy and Centre National d’Etudes Spaciales (CNES) in France for science analysis during the operations phase is also gratefully acknowledged. L.T. is partially supported by the International Doctorate on Astroparticle Physics (IDAPP) program. E.T is a NASA Postdoctoral Program Fellow.
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