- Conference date: 26–28 June 2012
- Location: Denver, Colorado, USA
Cosmic rays are thought to be accelerated at supernova remnant (SNR) shocks, but observation of the π0 bump that would confirm this expectation is hampered by weak γ-ray fluxes of SNRs, instrumental difficulties in observing lowenergy (≲ 100 MeV) emissions, background γrays made from cosmic-ray interactions with gas and dust in the vicinity of SNRs, leptonic γ rays, and γ-ray point sources. By contrast, cosmic-ray bombardment of nearby high-latitude gas located away from known molecular cloud complexes and with small ionized hydrogen column density along the line of sight provides a less confused emission region for study. The Large Area Telescope on the Fermi Gamma-ray Space Telescope has measured a γ-ray spectrum of high-latitude gas that reveals a low-energy cutoff corresponding to a π0 → 2γfeature . A shock-accelerated particle flux ∝ p −s , where p is the particle momentum, follows from simple theoretical considerations of cosmic-ray acceleration at nonrelativistic shocks followed by rigidity-dependent escape into the Galactic halo. A flux of shock-accelerated cosmic-ray protons with s ≈ 2.8 provides an adequate fit to the Fermi-LAT gamma-ray emission spectrum of high-latitude gas when uncertainties in secondary nuclear production models are taken into acount. The cosmicray spectrum inferred from the γ-ray emissivity spectrum is in accord with the SNR hypothesis for the origin of the cosmic rays .
- Supernova remnants
- Cosmic gamma ray sources
- Cosmic rays
- Gamma rays
- Gamma ray telescopes
Daniel Baumann, Mark G. Jackson, Peter Adshead, Alexandre Amblard, Amjad Ashoorioon, Nicola Bartolo, Rachel Bean, Maria Beltrán, Francesco de Bernardis, Simeon Bird, Xingang Chen, Daniel J. H. Chung, Loris Colombo, Asantha Cooray, Paolo Creminelli, Scott Dodelson, Joanna Dunkley, Cora Dvorkin, Richard Easther, Fabio Finelli, Raphael Flauger, Mark P. Hertzberg, Katherine Jones‐Smith, Shamit Kachru, Kenji Kadota, Justin Khoury, William H. Kinney, Eiichiro Komatsu, Lawrence M. Krauss, Julien Lesgourgues, Andrew Liddle, Michele Liguori, Eugene Lim, Andrei Linde, Sabino Matarrese, Harsh Mathur, Liam McAllister, Alessandro Melchiorri, Alberto Nicolis, Luca Pagano, Hiranya V. Peiris, Marco Peloso, Levon Pogosian, Elena Pierpaoli, Antonio Riotto, Uroš Seljak, Leonardo Senatore, Sarah Shandera, Eva Silverstein, Tristan Smith, Pascal Vaudrevange, Licia Verde, Ben Wandelt, David Wands, Scott Watson, Mark Wyman, Amit Yadav, Wessel Valkenburg and Matias Zaldarriaga
Data & Media loading...
Article metrics loading...