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Prospects of Identifying the Sources of the Galactic Cosmic Rays with IceCube

Prospects of Identifying the Sources of the Galactic Cosmic Rays with IceCube. Alexander Kappes Francis Halzen Aongus O’Murchadha University Wisconsin-Madison 3 rd VLVnT Workshop April 22. - 24. 2008, Toulon France. Outline. Cosmic rays and gamma/neutrino production

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Prospects of Identifying the Sources of the Galactic Cosmic Rays with IceCube

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  1. Prospects of Identifying the Sources of the Galactic Cosmic Rays with IceCube Alexander Kappes Francis Halzen Aongus O’Murchadha University Wisconsin-Madison 3rd VLVnT Workshop April 22. - 24. 2008, Toulon France

  2. Outline • Cosmic rays and gamma/neutrino production • Which are the accelerators of the Galactic cosmic rays? • Can we see them with neutrino telescopes (IceCube)? Alexander Kappes, 3rd VLVnT Workshop, Toulon France

  3. The Cosmic Ray Spectrum • Cosmic ray spectrum measured over more than 12 decades • Spectrum steepens at ~3 PeV • Transition between Galactic and extra-Galactic component at 1016 - 1018 eV • Form of spectrum requires Galactic accelerators up to 3 PeV (PeVatrons) • Not identifiable with cosmic ray experiments(magnetic fields) galactic extragalactic Alexander Kappes, 3rd VLVnT Workshop, Toulon France

  4. Hadronic neutrino and -ray production: p + p()→ p0 + X9 p + p()→ p + X9m+nm9 e + ne+nm ( ne: nm : nt )  (  :  : 0 Norm: Index: Cut-off: The Cosmic-Ray Gamma/Neutrino Connection • Relation  /  spectrum parameters (pp interactions)(at Earth   mixing leads to (1 : 1 : 1)) • Protons @ CR “knee” produce -rays of ~300 TeV Kappes etal: ApJ,656:870-896,2007 Alexander Kappes, 3rd VLVnT Workshop, Toulon France

  5. Gabici, Aharonian: arXiv:0705.3011 at 1 Kpc 400 yr 2000 yr 8000 yr (104 solar masses) 2000 yr 8000 yr 32000 yr Cherenkov telescopes (e.g. HESS, Magic) Air shower arrays(Milagro) The Mystery of the Missing PeVatrons • SNRs best candidates for Galactic cosmic ray accelerators • But no SNR  spectrum extends above a few 10 TeV • Possible reason: “Direct” high energy -ray emission only in first few hundred years • Detection still possible by observing secondary -rays produced in nearby clouds • Milagro better suited than Cherenkov telescopes Alexander Kappes, 3rd VLVnT Workshop, Toulon France

  6. MGRO J2031+41 MGRO J1852+01 MGRO J2019+37 VERITAS observation MGRO J1908+06 MGRO J2032+37 MGRO J2043+36 2007 Milagro Sky Survey At 12 TeV Abdo thesis defense, March 2007 • MGRO 2019+37: not seen by VERITAS in first observation consistency requires  < 2.2 • MGRO J2031+41: Magic measures E-2 spectrum Alexander Kappes, 3rd VLVnT Workshop, Toulon France

  7. Gamma-ray Spectrum of MGRO J1908+06 • Again E-2 spectrum;extends up to 100 TeV ! • Strong indicator of proton acceleration in this source Alexander Kappes, 3rd VLVnT Workshop, Toulon France

  8. The Role of Neutrino Telescopes • Air shower array currently only in Northern Hemisphere • Photon production ambiguous • Cherenkov telescopes have only small field of view (few deg2) • cover only small part of sky (at a time) • large photon background in star forming region (e.g. Cygnus)can hide sources • Neutrinos unambiguous sign for hadronic acceleration • Neutrino telescope properties fit well to air shower arrays • “all sky” sensitivity • increasing sensitivity with energy (small background) • angular resolution O(1º) Alexander Kappes, 3rd VLVnT Workshop, Toulon France

  9. Neutrino spectra for all sources Gamma and Neutrino Spectra Spectra for MGRO J1908+06 • Assumed E-2 with Milagro normaliztion (MGRO J1908+06 index = 2.1) • spectrum cutoff @ 180 TeV MGRO J1852+01 MGRO J2019+37 MGRO J1908+06 MGRO J2031+41MGRO J2043+36 MGRO J2032+37 10-11 10-10 E2flux (TeV s-1 cm-2) E2flux (TeV s-1 cm-2) 10-11 gamma flux 10-12 10-12 neutrino flux 10-13 10-13 1 1 10 1000 100 10 1000 100 Ethresh (TeV) Ethresh (TeV) Halzen, Kappes, O’Murchadha: arXiv:0803.0314 Alexander Kappes, 3rd VLVnT Workshop, Toulon France

  10. Significance for MGRO J1908+06 (5 years) • IceCube (80 strings) effective area (with quality cuts) • Search window: Halzen, Kappes, O’Murchadha: arXiv:0803.0314 1 # events p value observed events signal + atm.  10 2 calculated signal events 1 3 1 10 100 1 10 100 Ethresh (TeV) Ethresh (TeV) Milagro measurements favor lower sensitivity curve (dashed line) 2 - 2.5  after 5 years Alexander Kappes, 3rd VLVnT Workshop, Toulon France

  11. Significance for all 6 Milagro sources after 5 years Halzen, Kappes, O’Murchadha: arXiv:0803.0314 • p-value = 10-4 after 5 years but large error band (not shown) • Optimal threshold @ 30 TeV (determined by loss of signal events) Alexander Kappes, 3rd VLVnT Workshop, Toulon France

  12. # events (arb. units) Correlated Skymap Simulated Neutrino Skymaps IC80 (5 years) Not actual way to analyse data ! Alexander Kappes, 3rd VLVnT Workshop, Toulon France

  13. Summary • Cosmic ray sources (PeVatrons) should leave imprint on Milagro sky map • Milagro observes several hotspots with apparently hard spectra  maybe first PeVatron(s) discovered (MGRO J1908+06) • If these are the cosmic ray sources IceCube will be able to see them with time (best sensitivity above several 10 TeV) • MGRO J1852+01 and MGRO J1908+06 also visible (50%)by Mediterranean detectors More information in Halzen, Kappes, O’Murchadha: arXiv:0803.0314 Alexander Kappes, 3rd VLVnT Workshop, Toulon France

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