Planck constraint on relic primordial black holes
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2017 American Physical Society. We investigate constraints on the abundance of primordial black holes (PBHs) in the mass range 1015-1017 g using data from the cosmic microwave background (CMB) and MeV extragalactic gamma-ray background (EGB). Hawking radiation from PBHs with lifetime greater than the age of the Universe leaves an imprint on the CMB through modification of the ionization history and the damping of CMB anisotropies. Using a model for redshift-dependent energy injection efficiencies, we show that a combination of temperature and polarization data from Planck provides the strongest constraint on the abundance of PBHs for masses 1015-1016 g, while the EGB dominates for masses 1016 g. Both the CMB and EGB now rule out PBHs as the dominant component of dark matter for masses 1016-1017 g. Planned MeV gamma-ray observatories are ideal for further improving constraints on PBHs in this mass range.