Searching for Decaying and Annihilating Dark Matter with Line Intensity
  Mapping
  The purpose of line-intensity mapping (IM), an emerging tool for
extragalactic astronomy and cosmology, is to measure the integrated emission
along the line of sight from spectral lines emitted from galaxies and the
intergalactic medium. The observed frequency of the line then provides a
distance determination allowing the three-dimensional distribution of the
emitters to be mapped. Here we discuss the possibility to use these
measurements to seek radiative decays or annihilations from dark-matter
particles. The photons from monoenergetic decays will be correlated with the
mass distribution, which can be determined from galaxy surveys, weak-lensing
surveys, or the IM mapping experiments themselves. We discuss how to seek this
cross-correlation and then estimate the sensitivity of various IM experiments
in the dark-matter mass-lifetime parameter space. We find prospects for
improvements of ten orders of magnitude in sensitivity to decaying/annihilating
dark matter in the frequency bands targeted for IM experiments.
