Connecting blazars with ultrahigh-energy cosmic rays and astrophysical neutrinos

We present a strong hint of a connection between high-energy. gamma-ray emitting blazars, very high energy neutrinos, and ultrahigh-energy cosmic rays. We first identify potential hadronic sources by filtering gamma-ray emitters in spatial coincidence with the high-energy neutrinos detected by IceCube. The neutrino filtered. gamma-ray emitters are then correlated with the ultrahigh-energy cosmic rays from the Pierre Auger Observatory and the Telescope Array by scanning in gamma-ray flux (F-gamma) and angular separation (theta) between sources and cosmic rays. A maximal excess of 80 cosmic rays (42.5 expected) is found at theta <= 10 degrees from the neutrino-filtered. gamma-ray emitters selected from the second hard Fermi-LAT catalogue (2FHL) and for F-gamma(> 50 GeV) >= 1.8 x 10(-11) ph cm(-2) s(-1). The probability for this to happen is 2.4 x 10(-5), which translates to similar to 2.4x10(-3) after compensation for all the considered trials. No excess of cosmic rays is instead observed for the complement sample of gamma-ray emitters (i.e. not in spatial connection with IceCube neutrinos). A likelihood ratio test comparing the connection between the neutrinofiltered and the complement source samples with the cosmic rays favours a connection between neutrino-filtered emitters and cosmic rays with a probability of similar to 1.8 x 10(-3) (2.9 sigma) after compensation for all the considered trials. The neutrino-filtered gamma-ray sources that make up the cosmic rays excess are blazars of the high synchrotron peak type. More statistics is needed to further investigate these sources as candidate cosmic ray and neutrino emitters.