Constraining the origin of UHECRs and astrophysical neutrinos

We constrain properties of ultrahigh energy cosmic ray source environments (and potentially astrophysical neutrino sources), including their photon temperature, gas density, size, magnetic field strength and coherence length, using UHECR and neutrino spectra and composition. Some astrophysical source types which are consistent with a common origin of UHECRs and astrophysical neutrinos are presented. Under the common origin hypothesis, this analysis provides a new probe into the validity of hadronic interaction models.