  The latest IceCube data suggest that the all-flavor cosmic neutrino flux may
be as large as 10^-7 GeV/cm^2/s/sr around 30 TeV. We show that, if sources of
the TeV-PeV neutrinos are transparent to gamma rays with respect to two-photon
annihilation, strong tensions with the isotropic diffuse gamma-ray background
measured by Fermi are unavoidable, independently of the production mechanism.
We further show that, if the IceCube neutrinos have a photohadronic (pgamma)
origin, the sources are expected to be opaque to 1-100 GeV gamma rays. With
these general multimessenger arguments, we find that the latest data suggest a
population of cosmic-ray accelerators hidden in GeV-TeV gamma rays as a
neutrino origin. Searches for x-ray and MeV gamma-ray counterparts are
encouraged, and TeV-PeV neutrinos themselves will serve as special probes of
dense source environments.
