Constrains on the extragalactic origin of IceCube's neutrinos using HAWC
August 16, 2017
August 03, 2018
IceCube has discovered an unresolved and isotropic flux of neutrinos between 10 TeV and 8 PeV. Extragalactic origin for this flux is usually assumed, as well as a correlation with the sources of cosmic rays. To date, no clear association with a class of objects has been made. HAWC is a very-high-energy (VHE, or $\gtrsim$100~GeV) gamma ray observatory in operation in central Mexico. HAWC has studied 2/3 of the entire sky ($\sim8~sr)$. We use this survey to search for optically thin sources of cosmic rays and neutrinos, responsible for IceCube's observations.
We have written a simulation of the cosmological properties of neutrino sources, FIRESONG, to show that under certain conditions, HAWC should be observing multiple sources. However, HAWC has only detected 2 extragalactic objects in 760 days of livetime: Mrk 421 and Mrk 501. This deficiency of detected sources in the extragalactic sky can be used to constrain the properties of neutrino sources, such as their density in the local universe. The case HAWC restricts the most is for no evolution in the density of sources, in which at least 8 objects should have been detected for the cases not excluded already by IceCube.
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