Prospects of identifying the sources of the galactic cosmic rays with icecube
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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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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)?

Alexander Kappes, 3rd VLVnT Workshop, Toulon France


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


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


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


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


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


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


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


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


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


# events

(arb. units)

Correlated Skymap

Simulated Neutrino Skymaps IC80 (5 years)

Not actual way to analyse data !

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 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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