Primordial Black Holes as Coma Cluster Dark Matter and the Unresolved γ-Ray Background

If 0.1% of the dark matter (DM) in the Coma cluster is primordial black holes of mass between 1 and 100 × 10 −19 M ⊙ , then the GeV radiation from the cluster may be Hawking radiation. Dark Energy Survey has mapped the DM in the largest weak lensing maps so far produced. A correlation between the unresolved γ -ray background and large scale structure has been noted. This correlation might find a natural explanation if some of the DM is evaporating primordial black holes, but no correlation is seen. We draw attention to a cluster of Coma-like x-ray clusters, Draco X, at redshift 0.12.