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 , Toulon France

2. Alexander Kappes, 3rd VLVnT Workshop, 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

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 eV
Form of spectrum requires Galactic accelerators up to 3 PeV (PeVatrons)
Not identifiable with cosmic ray experiments (magnetic fields)
galactic
extragalactic
April 23, 2008
Alexander Kappes, 3rd VLVnT Workshop, Toulon France

4. The Cosmic-Ray Gamma/Neutrino Connection
p + p() → p + X m + nm e + ne + nm
p + p() → p0 + X  
Hadronic neutrino and -ray production:
( ne : nm : nt )  (  :  : 0
Relation  /  spectrum parameters (at Earth   mixing leads to (1 : 1 : 1))
CR “knee” produce -rays of ~300 TeV
Norm:
Index:
Cut-off:
Kappes etal: ApJ,656: ,2007
April 23, 2008
Alexander Kappes, 3rd VLVnT Workshop, Toulon France

5. The Mystery of the Missing PeVatrons
400 yr
2000 yr
8000 yr
32000 yr
(104 solar masses)
at 1 Kpc
Cherenkov telescopes
(e.g. HESS, Magic)
Air shower arrays (Milagro)
Gabici, Aharonian: arXiv:
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
April 23, 2008
Alexander Kappes, 3rd VLVnT Workshop, Toulon France

6. 2007 Milagro Sky Survey At 12 TeV
Abdo thesis defense, March 2007
TeV J
MAGIC: arXiv:
F = (4.5 ± 0.3) × E-2.0±0.3 (TeV-1 cm-2 s-1)
VERITAS observation
MGRO J
MGRO J
MGRO J
MGRO J
MGRO J
MGRO J
MGRO : not seen by VERITAS in first observation  consistency requires  < 2.2
MGRO J : Magic measures E-2 spectrum
April 23, 2008
Alexander Kappes, 3rd VLVnT Workshop, Toulon France

7. Gamma-ray Spectrum of MGRO J1908+06
preliminary 60 90
Revised H.E.S.S. flux now factor 2 lower !
Sabrina Heidelberg workshop, Jan 2008
E (TeV)
Again E-2 spectrum; extends up to 100 TeV !
Strong indicator of proton acceleration in this source
April 23, 2008
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)
April 23, 2008
Alexander Kappes, 3rd VLVnT Workshop, Toulon France

9. Gamma and Neutrino Spectra
Spectra for MGRO J
Neutrino spectra for all sources
MGRO J
MGRO J
MGRO J
MGRO J MGRO J
MGRO J
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 10
100
1000 1 10
100
1000
Ethresh (TeV)
Ethresh (TeV)
Halzen, Kappes, O’Murchadha: arXiv:
Assumed E-2 with Milagro normaliztion (MGRO J index = 2.1)
spectrum 180 TeV
April 23, 2008
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: 1
# events
p value 10
observed events 2
calculated signal events 1 3 1 10
100
Ethresh (TeV) 1 10
100
Ethresh (TeV)
Milagro measurements favor lower sensitivity curve (dashed line)   after 5 years
April 23, 2008
Alexander Kappes, 3rd VLVnT Workshop, Toulon France

11. Significance for all 6 Milagro sources after 5 years
Halzen, Kappes, O’Murchadha: arXiv:
p-value = 10-4 after 5 years but large error band (not shown)
Optimal 30 TeV (determined by loss of signal events)
April 23, 2008
Alexander Kappes, 3rd VLVnT Workshop, Toulon France

12. Simulated Neutrino Skymaps IC80 (5 years)
# events
(arb. units)
Correlated Skymap
April 23, 2008
Alexander Kappes, 3rd VLVnT Workshop, Toulon France

13. Alexander Kappes, 3rd VLVnT Workshop, Toulon France
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 J )
If these are the cosmic ray sources IceCube will be able to see them after several years (best sensitivity above several 10 TeV)
MGRO J and MGRO J also visible (50%) by Mediterranean detectors
April 23, 2008
Alexander Kappes, 3rd VLVnT Workshop, Toulon France