How do we image dark matter?

(a) We see light from galaxies behind the bullet cluster that is bent (gravitationally lensed)
due to the matter (regular and dark) in the bullet cluster.
(b) We see light from the gas in the two bullet cluster galaxies and we observe that the gas
is moved due to the pull of dark matter.
(c) We see light from dark matter annihilation to photons (or to other particles which
subsequently produce light).
(d) We see light from Type-1a supernovas which resulted from two stars being pulled close
to each other due to dark matter.

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