CMB constraints on ultralight primordial black holes with extended mass distributions
Abstract
We examine the effects ultralight primordial black holes (PBHs) have on the anisotropies of the cosmic microwave background (CMB). PBHs in the mass range of $10^{15}$ to $10^{17}$ g emit Hawking radiation in the early Universe, modifying the standard recombination history. This leads to a damping of smallscale temperature and polarisation anisotropies and enhances largescale polarisation fluctuations. As some models of inflation predict PBHs with a range of masses, we investigate the impacts of extended mass distributions on PBH abundance constraints. We model PBH energy injection using a groundup approach incorporating speciesdependent deposition efficiencies. By allowing the $\Lambda$CDM parameters to vary simultaneously with the PBH fraction and mass, we show that exclusion bounds on the PBH fraction of DM $f_\text{PBH}$ are relaxed by up to an order of magnitude, compared to the case of fixed $\Lambda$CDM parameters. We also give 95% exclusion regions for $f_\text{PBH}$ for a variety of mass distributions. In particular, for a uniform mass distribution between $10^{15}$ and $10^{17}$ g, we find $f_\text{PBH} < 1.6 \times 10^{5}$ when allowing $\Lambda$CDM parameters to vary.
 Publication:

arXiv eprints
 Pub Date:
 July 2019
 DOI:
 10.48550/arXiv.1907.06485
 arXiv:
 arXiv:1907.06485
 Bibcode:
 2019arXiv190706485P
 Keywords:

 Astrophysics  Cosmology and Nongalactic Astrophysics;
 High Energy Physics  Phenomenology