Constraints to a Galactic Component of the Ice Cube cosmic neutrino flux from ANTARES

Abstract

The IceCube evidence for cosmic neutrinos in the high-energy starting events (HESE) sample has inspired a large number of hypothesis on their origin, mainly due to the poor precision on the measurement of the direction of showering events. The fact that most of HESE are downward going suggests a possible Galactic component. This could be originated either by a single point-like source or to a directional excess from an extended Galactic region. These hypotheses are reviewed and constrained, using the present available upper limits from the ANTARES neutrino telescope. ANTARES detects $\nu_\mu$ from sources in the Southern sky with an effective area larger than that providing the IceCube HESE for $E_\nu<60$ TeV and a factor of about two smaller at 1 PeV. The use of the $\nu_\mu$ signal enables an accurate measurement of the incoming neutrino direction. The Galactic signal allowed by the IceCube HESE and the corresponding ANTARES limits are studied in terms of a power law flux $E^{-\Gamma}$, with spectral index $\Gamma$ ranging from 2.0 to 2.5 to cover most astrophysical models.