Gam Gamma- ma-Ra Ray Ob y Obse servatio ions ns � of f Supernova Rem emnants � 1 Patrick Slane 4th Fermi Asian Network Workshop 9 July 2013
Cosmic Rays and SNRs � • CR spectrum is a power law covering � more than 10 decades in energy. � - “knee” in spectrum at ~10 15-16 eV � Extragalactic - CRs below knee thought to be � Solar Modulation Galactic in origin � knee • Composition of Galactic CRs similar � to well-mixed ISM � - energy density ∼ 1 eV cm -3 � • Direct evidence of CR acceleration � provides opportunity to constrain � Galactic acceleration physics and address � source of CRs � - multi- λ observations are crucial � for source/counterpart identification, � constraining emission geometry, � probing source environment, and � breaking modeling degeneracies � 2 Patrick Slane 4th Fermi Asian Network Workshop 9 July 2013
Diffusive Shock Acceleration � • Particles scatter from MHD � waves in background plasma � - pre-existing, or generated � by streaming ions themselves � - scattering mean-free-path � λ ∝ r g = E / eB (i.e., most energetic particles � have very large λ and escape) � Reynolds 2008 � ρ 2 ~E -2.2 (p -4.2 ) ρ 1 3 Patrick Slane 4th Fermi Asian Network Workshop 9 July 2013
Gamma-Ray Emission from SNRs � • Inverse-Compton � - energetic electrons � upscatter ambient � photons to γ -ray � energies � - also produce synchrotron � 4 Patrick Slane 4th Fermi Asian Network Workshop 9 July 2013
Gamma-Ray Emission from SNRs � • Inverse-Compton � - energetic electrons � upscatter ambient � photons to γ -ray � energies � - also produce synchrotron � • Nonthermal bremsstrahlung � - energetic electrons � decelerated by collisons � w/ ions � 5 Patrick Slane 4th Fermi Asian Network Workshop 9 July 2013
Gamma-Ray Emission from SNRs � • Inverse-Compton � - energetic electrons � upscatter ambient � photons to γ -ray � energies � - also produce synchrotron � • Nonthermal bremsstrahlung � - energetic electrons � decelerated by collisons � w/ ions � • Neutral pion decay: � π 0 → γγ � - flux proportional � to ambient density; � SNR-cloud interactions � particularly likely sites � 6 Patrick Slane 4th Fermi Asian Network Workshop 9 July 2013
Gamma-Ray Emission from SNRs � • Inverse-Compton � - energetic electrons � upscatter ambient � photons to γ -ray � energies � - also produce synchrotron � • Nonthermal bremsstrahlung � - energetic electrons � decelerated by collisons � w/ ions � • Neutral pion decay: � π 0 → γγ � - flux proportional � to ambient density; � SNR-cloud interactions � particularly likely sites � Castro et al. 2013 � 7 Patrick Slane 4th Fermi Asian Network Workshop 9 July 2013
Modeling: CR-Hydro � • Semi-analytical calculation of DSA � • VH-1 hydrodynamics code to follow � SNR evolution � • NEI calculation of ionization fractions � from hydro � • Plasma emissivity code for spectra � • Emission from superthermal/relativistic � particles � - synchrotron � - inverse Compton � - nonthermal bremsstrahlung � - pion-decay � " " " Ellison et al. 2007 � " " " Patnaude et al. 2009 � " " " Ellison et al. 2010 � " " " Patnaude et al. 2010 � 8 Patrick Slane 4th Fermi Asian Network Workshop 9 July 2013
Gamma-Rays from SNRs � 9 Patrick Slane 4th Fermi Asian Network Workshop 9 July 2013
G347 .3-0.5/RX J1713.7 -3946 � • X-ray observations reveal � Aharonian et al. 2004 � H.E.S.S. � nonthermal spectrum � - no hint of thermal emission � 10 Patrick Slane 4th Fermi Asian Network Workshop 9 July 2013
G347 .3-0.5/RX J1713.7 -3946 � • X-ray observations reveal � nonthermal spectrum � - no hint of thermal emission � • Broadband emission can be fit � with hadronic or leptonic � models � - hadronic model predicts � bright thermal X-rays, � which are not observed � - γ -rays dominated by leptons � NOTE: Hadrons are accelerated; they dominate the energy. � Ellison et al. 2010 � 11 Patrick Slane 4th Fermi Asian Network Workshop 9 July 2013
G347 .3-0.5/RX J1713.7 -3946 � • X-ray observations reveal � nonthermal spectrum � - no hint of thermal emission � • Broadband emission can be fit � with hadronic or leptonic � models � - hadronic model predicts � bright thermal X-rays, � which are not observed � - γ -rays dominated by leptons � NOTE: Hadrons are accelerated; they dominate the energy. � • Hadrons could dominate γ -rays � if shell consists of many cold � Inoue et al. 2012 � clumps in interclump medium � 12 Patrick Slane 4th Fermi Asian Network Workshop 9 July 2013
Gamma-Rays from Tycho’ s SNR � • Tycho’ s SNR is shows strong dynamical � evidence for CR acceleration � Warren et al. 2005 � 13 Patrick Slane 4th Fermi Asian Network Workshop 9 July 2013
Gamma-Rays from Tycho’ s SNR � Acciari et al. 2011 � • Tycho’ s SNR is shows strong dynamical � evidence for CR acceleration � • Tycho is also detected in γ -rays � - VERITAS centroid appears shifted � slightly toward molecular cloud � 14 Patrick Slane 4th Fermi Asian Network Workshop 9 July 2013
Gamma-Rays from Tycho’ s SNR � Acciari et al. 2011 � • Tycho’ s SNR is shows strong dynamical � evidence for CR acceleration � • Tycho is also detected in γ -rays � - VERITAS centroid appears shifted � slightly toward molecular cloud � • Both hadronic and leptonic models � can reproduce broadband spectrum � 15 Patrick Slane 4th Fermi Asian Network Workshop 9 July 2013
Gamma-Rays from Tycho’ s SNR � Giordano et al. 2012 � • Tycho’ s SNR is shows strong dynamical � evidence for CR acceleration � • Tycho is also detected in γ -rays � - VERITAS centroid appears shifted � slightly toward molecular cloud � • Both hadronic and leptonic models � can reproduce broadband spectrum � • Fermi detection strongly favors � hadrons as primary source of γ -rays � 16 Patrick Slane 4th Fermi Asian Network Workshop 9 July 2013
SNRs Interacting w/ Molecular Clouds � Uchiyama et al. 2011 � • SNRs with maser � emission interacting � with molecular clouds � - likely sources of � γ -ray emission � • Fermi/LAT detects � GeV emission from � several SNRs with � masers � - inferred density � much higher than � X-rays indicate � - may imply clumping � or escaping cosmic- � ray population that � is interacting with � nearby clouds � 17 Patrick Slane 4th Fermi Asian Network Workshop 9 July 2013
SNRs Interacting w/ Molecular Clouds � Castro & Slane 2010 � G349.7+0.2 � CTB 37A � • SNRs with maser � emission interacting � with molecular clouds � - likely sources of � γ -ray emission � • Fermi/LAT detects � GeV emission from � several SNRs with � masers � 3C 391 � G8.7-0.1 � - inferred density � much higher than � X-rays indicate � - may imply clumping � or escaping cosmic- � ray population that � is interacting with � nearby clouds � 18 Patrick Slane 4th Fermi Asian Network Workshop 9 July 2013
SNRs Interacting w/ Molecular Clouds � Castro et al. 2013 � W41 � G337 .7-0.1 � • SNRs with maser � emission interacting � with molecular clouds � - likely sources of � γ -ray emission � • Fermi/LAT detects � GeV emission from � several SNRs with � masers � MSH 17-39 � Kes 79 � - inferred density � much higher than � X-rays indicate � - may imply clumping � or escaping cosmic- � ray population that � is interacting with � nearby clouds � Auchettl et al. 2013 � 19 Patrick Slane 4th Fermi Asian Network Workshop 9 July 2013
SNRs in Dense Environments: 3C 391 � • 3C 391 shows distinct evidence of � of MC interaction � Chen et al. (2004) � - bright, flattened radio morphology � - adjacent CO cloud � - OH masers � 20 Patrick Slane 4th Fermi Asian Network Workshop 9 July 2013
SNRs in Dense Environments: 3C 391 � • 3C 391 shows distinct evidence of � of MC interaction � - bright, flattened radio morphology � - adjacent CO cloud � - OH masers � 21 Patrick Slane 4th Fermi Asian Network Workshop 9 July 2013
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