ANTARES constrains the extension of a possible High Energy Neutrino source near the Galactic Centre

[Published April 2014]

The results of an updated search for cosmic neutrino sources using six years of data collected by the ANTARES neutrino telescope has been recently published. The most signal-like accumulation of events is located at equatorial coordinates RA=-46.8 and Dec=-64.9 and corresponds to a 2.2σ background fluctuation. In addition, upper limits on the flux normalization of an E-2 muon neutrino energy spectrum have been set for 50 pre-selected astrophysical objects.

Left : 90 % C.L. flux upper limits and sensitivities on the muon neutrino flux for six years of ANTARES data. IceCube results are also shown for comparison. The light-blue markers show the upper limit for any point source located in the ANTARES visible sky in declination bands of 1. The solid blue (red) line indicates the ANTARES (IceCube) sensitivity for a point-source with an E-2 spectrum as a function of the declination. The blue (red) squares represent the upper limits for the ANTARES (IceCube) candidate sources.  Finally, the dashed dark blue (red) line indicates the ANTARES (IceCube) sensitivity for a point-source and for neutrino energies lower than 100 TeV, which shows that the IceCube sensitivity for sources in the Southern hemisphere is mostly due to events of higher energy. IceCube results from this reference.
Finally, motivated by an accumulation of 7 events relatively close to the Galactic Centre in the recently reported neutrino sample of the IceCube telescope, a search for point sources in a broad region around this accumulation has been carried out. A point source close to the Galactic Centre has been recently proposed to explain this accumulation of events (see this publication) ; the absence of a significant neutrino signal detected by ANTARES in these directions has allowed us to exclude a single point source (width = 0) as being the emitter of these events. Constraints on extended sources have also been set.

Left : 90 % C.L. upper limits obtained for different source widths as a function of the declination.  The blue horizontal dashed line corresponds to the signal flux given by these authors.