Transcript ppt

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
Outline
 Cosmic rays and gamma/neutrino production
 Which are the accelerators of the Galactic cosmic rays?
 Can we see them with neutrino telescopes (IceCube)?
April 23, 2008
Alexander Kappes, 3rd VLVnT Workshop, Toulon France
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The Cosmic Ray Spectrum
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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
galactic
extragalactic
Form of spectrum requires
Galactic accelerators up to
3 PeV (PeVatrons)
Not identifiable with cosmic
ray experiments
(magnetic fields)
April 23, 2008
Alexander Kappes, 3rd VLVnT Workshop, Toulon France
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The Cosmic-Ray Gamma/Neutrino Connection
Hadronic neutrino and -ray production:
0
p + p() → p + X
p + p() → p + X
9 
9 m + m
9 e + e + m
( e : m : t )  (  :  : 0 )
 Relation  /  spectrum parameters (pp interactions)
(at Earth   mixing leads to (1 : 1 : 1))
Norm:
Index:
Cut-off:
Kappes etal: ApJ,656:870-896,2007
 Protons @ CR “knee” produce -rays of ~300 TeV
April 23, 2008
Alexander Kappes, 3rd VLVnT Workshop, Toulon France
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The Mystery of the Missing PeVatrons
Gabici, Aharonian: arXiv:0705.3011
 SNRs best candidates for
Galactic cosmic ray
accelerators
 But no SNR  spectrum
extends above a few 10 TeV
at 1 Kpc
400 yr
2000 yr
8000 yr
 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
April 23, 2008
(104 solar masses)
2000 yr
8000 yr
32000 yr
Cherenkov telescopes
(e.g. HESS, Magic)
Air shower arrays
(Milagro)
Alexander Kappes, 3rd VLVnT Workshop, Toulon France
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2007 Milagro Sky Survey At 12 TeV
Abdo thesis defense, March 2007
MGRO J2031+41
MGRO J1852+01
MGRO J2019+37
MGRO J1908+06
VERITAS observation
MGRO J2043+36 MGRO J2032+37
 MGRO 2019+37: not seen by VERITAS in first observation
 consistency requires  < 2.2
 MGRO J2031+41: Magic measures E-2 spectrum
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Gamma-ray Spectrum of MGRO J1908+06
 Again E-2 spectrum; extends up to 100 TeV !
 Strong indicator of proton acceleration in this source
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Alexander Kappes, 3rd VLVnT Workshop, Toulon France
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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)
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Alexander Kappes, 3rd VLVnT Workshop, Toulon France
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Gamma and Neutrino Spectra
Neutrino spectra for all sources
E2flux (TeV s-1 cm-2)
E2flux (TeV s-1 cm-2)
Spectra for MGRO J1908+06
MGRO J1852+01
MGRO J2019+37
MGRO J1908+06
MGRO J2031+41
MGRO J2043+36
MGRO J2032+37
10-11
10-10
10-11
gamma flux
10-12
10-12
neutrino flux
10-13
1
10
1000
100
Ethresh (TeV)
10-13
1
10
1000
100
Ethresh (TeV)
Halzen, Kappes, O’Murchadha: arXiv:0803.0314
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Assumed E-2 with Milagro normaliztion (MGRO J1908+06 index = 2.1)
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 spectrum cutoff @ 180 TeV
April 23, 2008
Alexander Kappes, 3rd VLVnT Workshop, Toulon France
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Significance for MGRO J1908+06 (5 years)
IceCube (80 strings) effective area (with quality cuts)
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2
2
Search window: 1.6  rsrc
 rres

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Halzen, Kappes, O’Murchadha: arXiv:0803.0314
p value
# events
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1
observed events
signal + atm. 
2
calculated
signal events
1
3
1
10
100
Ethresh (TeV)
1
10
100
Ethresh (TeV)
Milagro measurements favor lower sensitivity curve (dashed line)
 2 - 2.5  after 5 years
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Significance for all 6 Milagro sources after 5 years
Halzen, Kappes, O’Murchadha: arXiv:0803.0314
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p-value = 10-4 after 5 years but large error band (not shown)
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Optimal threshold @ 30 TeV (determined by loss of signal events)
April 23, 2008
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Simulated Neutrino Skymaps IC80 (5 years)
Correlated Skymap
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# events
(arb. units)
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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
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