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Studies of Cosmic-ray Acceleration with Cosmic Gamma-ray

Studies of Cosmic-ray Acceleration with Cosmic Gamma-ray. Outline. Introduction. Gamma-ray detectors. SNR Galaxy cluster GRB. Cosmic Particle Accelerators. Origin of cosmic ray protons?

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Studies of Cosmic-ray Acceleration with Cosmic Gamma-ray

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  1. Studies of Cosmic-ray Acceleration with Cosmic Gamma-ray Outline • Introduction. • Gamma-ray detectors. • SNR • Galaxy cluster • GRB

  2. Cosmic Particle Accelerators • Origin of cosmic ray protons? • Galactic SNRs (Supernova Remnants) are considered as the best candidates for cosmic-rays below “Knee”. • Only circumstantial evidence • Diffusive shock acceleration. (Blanford&Eichler 1977) • CR energy sum consistent with SNR kinetic energy. (Ginzburg&Syrovatskii 1964) • No observational evidencefor hadronic acceleration. • Cosmic-rays above “Knee” are considered extragalactic. • Gamma-ray bursts (GRB). • Active Galactic Nuclei. • Galaxy clusters. Cosmic-ray Accelerators, H. Tajima, DPF/JPS 2006, OCT. 31, 2006

  3. Why Gamma-rays? • Charged particles are bent by interstellar magnetic field. • Requires E>1019 eV for straight propagation. • Neutral particles • Neutrino: not sufficient sensitivity • Photon • Radio, Optical, X-ray: thermal emission dominant • Gamma-ray: high energy particle origin Cosmic-ray Accelerators, H. Tajima, DPF/JPS 2006, OCT. 31, 2006

  4. Hadronic Cosmic-ray Interactions (CMB) (Cosmic Microwave Background)  Compton scattering e+e– p π0 (CMB) π± →µ±→e± p p (Inter stellar medium) Cosmic-ray Accelerators, H. Tajima, DPF/JPS 2006, OCT. 31, 2006

  5. Gamma-ray Emission from Electrons • Synchrotron radiation. • E-p➯ε-(p-1)/2 • Polarization. • Cut off energy: • Compton Scattering. • Up-scatter cosmic microwave BKG. • E-p➯ε-(p-1)/2 Electron distribution N(g) g -p cooling g -p-1 gmin g gc Fn Energy spectrum n 1/3 n -(p-1)/2 Fn self absorption n 2 n 1/3 Emission from a single electron n -p/2 na nm nc n G. Sato Cosmic-ray Accelerators, H. Tajima, DPF/JPS 2006, OCT. 31, 2006

  6. Gamma-ray Emission from Hadrons • Interaction with matters. • Bremsstrahlung. • E < Ecou: ε-1 (independent of parent energy spectrum). • E > Ecou: E-p➯ε-p (no change). • Ecou: • εcou (p)=me/mpEcou, εcou (e) = Ecou. • π0 decays. • E-p➯ε-p (no change). • π±→ µ±→e± • Synchrotron, Compton Uchiyama et al. π → µ → e synchrotron π0 decays Aharonian Cosmic-ray Accelerators, H. Tajima, DPF/JPS 2006, OCT. 31, 2006

  7. e– e+ Gamma-ray Detectors Cosmic-ray Accelerators, H. Tajima, DPF/JPS 2006, OCT. 31, 2006

  8. GLAST LAT Instrument • Tracker: conversion, tracking. • Angular resolution is dominated by scattering. • Converter thickness optimization. • Calorimeter: energy measurement. • 8.4 radiation length. • Use shower development to compensate for the leak. • Anti-coincidence detector: • Efficiency > 99.97%. Si Tracker 90 m2 , 228 µm pitch ~0.9 million channels g e- e+ Anti-coincidence Detector Segmented scintillator tiles 99.97% efficiency CsI Calorimeter 8.4 radiation length Cosmic-ray Accelerators, H. Tajima, DPF/JPS 2006, OCT. 31, 2006

  9. Water Cherenkov Air Shower array • Good hadronic shower rejection. • 900 PMTs with 3 m spacing. • ~100% coverage of all incoming particles. • Reconstruct shower direction from arrival time difference. Milagro Cosmic-ray Accelerators, H. Tajima, DPF/JPS 2006, OCT. 31, 2006

  10. Atmospheric Cherenkov Telescopes • Image Cherenkov lights from air showers • Mirror size: 10 – 17 m • Bigger mirror → lower energy threshold • 2 or more telescopes for CR rejection • 500–1000 PMTS at focal plane VERITAS HESS MAGIC Cosmic-ray Accelerators, H. Tajima, DPF/JPS 2006, OCT. 31, 2006

  11. ACT Background Rejection Four telescope mode: HESS since December 2003. CANGAROO March 2004. VERITAS Early 2007. MAGIC (2 telescope) Fall 2007. • Shower shape: 10-3 • Shower coincidence: 10-2 VERITAS (Krennrich) CANGAROO Cosmic-ray Accelerators, H. Tajima, DPF/JPS 2006, OCT. 31, 2006

  12. TeV Gamma-ray from SNR • HESS TeV gamma-ray observation of RX J1713-3946 • Evidence for particle acceleration > 100 TeV. • Morphological similarity with X-ray observation. • Azimuth profile does not match very well with molecular clouds. • Suggest leptonic origin? – TeV gamma-ray – Molecular clouds HESS/ASCA Aharonian et al. 2005 – TeV gamma-ray – X-ray (1-5 keV) – X-ray (5-10 keV) Cosmic-ray Accelerators, H. Tajima, DPF/JPS 2006, OCT. 31, 2006

  13. Gamma-ray Spectrum for RX J1713 • HESS spectrum may prefer hadronic origin. • Not conclusive. • Gamm-rays from π0 decays due to hadronic interaction with molecular clouds Berezhko 2006 & Aharonian et al. 2005 Bd = 126 µG Kep = 10-4 ESN = 1.8 x1051 erg age = 1600 year Model independent (π0 production and decay kinematics) — pp→π0→, — Inverse Compton (B=9µG) — Inverse Compton (B=7µG) Cosmic-ray Accelerators, H. Tajima, DPF/JPS 2006, OCT. 31, 2006

  14. Expected GLAST Spectrum for J1713 • Preliminary results on simulated 5-year GLAST observation of RX J1713-3946. • GLAST can positively identify hadronic contribution. Funk Cosmic-ray Accelerators, H. Tajima, DPF/JPS 2006, OCT. 31, 2006

  15. HESS Observation of Vela Jr Hadronic model • Leptonic model gives better fit for both X-ray and TeV -ray Leptonic model D. Horn (HESS) Cosmic-ray Accelerators, H. Tajima, DPF/JPS 2006, OCT. 31, 2006

  16. TeV Gamma-ray SNR Candidates 25% Crab 19% Crab 5% Crab 6% Crab 8% Crab 13% Crab HESS ApJ 636 (2006) 777 Cosmic-ray Accelerators, H. Tajima, DPF/JPS 2006, OCT. 31, 2006

  17. -rays from Merging Galaxy Cluster • Strong shock due minor merger of galaxy clusters. • Model parameters are tuned to be consistent with existing measurements. • Particle acceleration up to 1019 eV. (Origin of UHE-CR?) • Secondary e+e- following proton interaction with CMB photon are dominant origin of gamma-rays. Inoue 2005 ApJ 628, L9 Milagro GLAST VERITAS GLAST can detect IC from secondary e+e- merging galaxy group Cosmic-ray Accelerators, H. Tajima, DPF/JPS 2006, OCT. 31, 2006

  18. GRB Delayed Gamma-ray Emission Gonzalez, Nature 2003 424, 749 • Delayed gamma-ray emission from GRB is observed by EGRET. • It is hard to explain by conventional electron synchrotron models. • Proton acceleration? Origin of UHECR? • More samples required to understand further. • GLAST will add much more samples. • GLAST extend the energy reach to ~200 GeV. • Broadband spectra constrain emission models. -18 - 14s EGRET/TASC BATSE 14 - 47s 47 - 80s 80 - 113s Total Absorption Shower Counter 113 - 211s Cosmic-ray Accelerators, H. Tajima, DPF/JPS 2006, OCT. 31, 2006

  19. Milagro Observation of GRB970417a • Milagro looked at 54 GRBs observed by BATSE. • GRB970417a inconsistent with background. • 18 photon observed for 3.4 expected BG. • 99.8% confidence level. Atkins, R., et al., Ap J Lett, Vol 533, L119 Cosmic-ray Accelerators, H. Tajima, DPF/JPS 2006, OCT. 31, 2006

  20. Summary • Origin of cosmic-rays is still mystery. • SNR is the most promising site for cosmic-ray acceleration. • HESS provided undisputed evidence for >100 TeV particle acceleration. • GLAST will provideconclusive proof on the origin of gamma-rays from SNR, RX J1713-3946 and Vela Jr. • More SNRs will be observed by ACT and GLAST. • Emerging extra-Galactic sources. • Constraints on models of particle acceleration in merging galaxies and galaxy clusters. • Coma observation of VERITAS and/or GLAST. • More gamma-ray observation of GRBs by GLAST/HAWC(?). Cosmic-ray Accelerators, H. Tajima, DPF/JPS 2006, OCT. 31, 2006

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