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Constraints to a Galactic component of the IceCube cosmic neutrino flux

Constraints to a Galactic component of the IceCube cosmic neutrino flux. Maurizio Spurio. Visioconference 4/9/2014. Starting motivation. Comparison between A eff. Different selection criteria IceCube = 4 p , high energy sample (E n >30 TeV ), almost bck free

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Constraints to a Galactic component of the IceCube cosmic neutrino flux

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  1. Constraints to a Galactic component of the IceCube cosmic neutrino flux Constraint to a Galactic IceCube signal - M. Spurio Maurizio Spurio Visioconference 4/9/2014

  2. Starting motivation Constraint to a Galactic IceCube signal - M. Spurio

  3. ComparisonbetweenAeff Constraint to a Galactic IceCube signal - M. Spurio • Differentselectioncriteria • IceCube = 4p, high energy sample (En>30 TeV), almostbck free • ANTARES= nmonly, southernsky, lowerenergy

  4. Details: see Constraint to a Galactic IceCube signal - M. Spurio

  5. The IceCube HESE • It is possible, using the effective area, to obtain the normalization factor FD,Gfor any other spectral index G. • We computed the values of FD,G for G from 2.0 to 2.5 • This extend the possible range of astrophysical models for the signal • In particular, we are interested on a possible Galactic component From IceCube arXiv:1405.5303 Constraint to a Galactic IceCube signal - M. Spurio

  6. The normalizationfactors • Valid for a generic E-G spectrum • Derived from the IC effective areas Constraint to a Galactic IceCube signal - M. Spurio

  7. A galactic component in HESE • A Galactic component is quoted statistically non-signicant by the IceCube collaboration; • The expected signal from the Northern hemisphere (purely extragalactic) is a factor of 2 larger than measured; • Assuming 3.6 Up and symmetric extragalactic contribution, the expected Down HESE of extragalactic origin are: =6.2 (5.8) events for the E-2.0 (E-2.5) spectrum. • Galactic contribution= 13.7-6.2  7.5 events Constraint to a Galactic IceCube signal - M. Spurio

  8. I) A point-likeGalactic source • Signal due to a point like source • np events out NIC are due to this source, with energy spectrum: • The normalization factor can be derived with the use of the Aeff (E) Constraint to a Galactic IceCube signal - M. Spurio • The normalization factor depends on the diffuse normalization factor (for G=2.0 , that reported in the IceCube paper) Same formula in:

  9. ANTARES hasupperbounds For different energy spectra E-G: Constraint to a Galactic IceCube signal - M. Spurio

  10. Results Constraint to a Galactic IceCube signal - M. Spurio • The ANTARES 90% C.L. upper limit excludes that a single point-like source produces more than 5 IceCube events, assuming a spectral index G=2.0. • A single point-like source yielding a cluster of more than 2 events is excluded for G=2.3 • A clusters made of two or more events is excluded for G> 2.3.

  11. II) Enhanced diffuse Galactic source • Signal due to a extended source, comparable with the IC angular resolution • Size DW much larger than the ANTARES angular resolution • nDW events out NIC are due to this source, with energy spectrum: DW Constraint to a Galactic IceCube signal - M. Spurio

  12. Predictions (nDW, DW) vs. G Constraint to a Galactic IceCube signal - M. Spurio

  13. ANTARES bounds? • At present, missing constraints; • Problem: for an extended source, large background of atmospheric neutrinos (50 events in a 8° radius); • Strategy: suppress the atmospheric neutrinos using the muon estimated energy • Method alreadyused in the FB analysis • Sensitivity: Constraint to a Galactic IceCube signal - M. Spurio

  14. Constraint to a Galactic IceCube signal - M. Spurio

  15. Perspectives • Itassumes the sameoptimizationas for the FB analysis for anyspectralindexG; • Signal/noiseimproveswhen the searchsolid angle decreases 8° 20° Constraint to a Galactic IceCube signal - M. Spurio

  16. Conclusions • The galactic component in the HESE sample is quantitatively estimated (it could be over-fluctuation…) • Due to the similarity on the IC/ANTARES effective areas, a point-like signal or an enhanced diffuse signal in the Galaxy can be seen/excluded by ANTARES • 1) Source association(Padovani/Resconi style). See considerations in the Antoine talk • 2) Presence of a point-like source. Upper limits already published by ANTARES constrain severly some hypothesis, in particular for energy spectra E-G with G>2.2 • 3) Extended source, seen as an enhanced diffuse flux. • Redo an analysis similar to that of the FB centered on the IC hot spot and with windows 0.06 sr (8°) and 0.38 sr (20°) Constraint to a Galactic IceCube signal - M. Spurio

  17. Whatabout the safe «twoorders on magnitudes»? • The statement is (in my opinion) a signal of the habit to understimate ANTARES (a factor of 40 in effective volume…); • The crucialpoint to a possibleverification/falsification of the IC signal by ANTARES is the presence of a Galactic component • The statement on JHEA is due to an error in the formula for the computation of the directionalflux in Table 3 (DW=0.06 sr) and Table 4 (DW=0.38 sr) : • whichisincorrect by a factor of • = 209 for Table 3 • = 33 for Table 4 Constraint to a Galactic IceCube signal - M. Spurio

  18. Lets observe a signal, if a real Galactic component is present in the HESE sample Constraint to a Galactic IceCube signal - M. Spurio

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