Probing relic neutrino decays with 21 cm cosmology
  We show how 21 cm cosmology can test relic neutrino radiative decays into
sterile neutrinos. Using recent EDGES results, we derive constraints on the
lifetime of the decaying neutrinos. If the EDGES anomaly will be confirmed,
then there are two solutions, one for much longer and one for much shorter
lifetimes than the age of the universe, showing how relic neutrino radiative
decays can explain the anomaly in a simple way. We also show how to combine
EDGES results with those from radio background observations, showing that
potentially the ARCADE 2 excess can be also reproduced together with the EDGES
anomaly within the proposed non-standard cosmological scenario. Our calculation
of the specific intensity at the redshifts probed by EDGES can be also applied
to the case of decaying dark matter and it also corrects a flawed expression
appeared in previous literature.
