The renewed interest in the possibility that primordial black holes ( PBHs ) may constitute a significant part of the dark matter has motivated revisiting old observational constraints , as well as developing new ones .
We present new limits on the PBH abundance , from a comprehensive analysis of high-resolution , high-redshift Lyman- \alpha forest data .
Poisson fluctuations in the PBH number density induce a small-scale power enhancement which departs from the standard cold dark matter prediction .
Using a grid of hydrodynamic simulations exploring different values of astrophysical parameters , we obtain a marginalized upper limit on the PBH mass of f _ { PBH } M _ { PBH } \sim 60 ~ { } M _ { \odot } at 2 \sigma , when a Gaussian prior on the reionization redshift is imposed , preventing its posterior distribution to peak on very high values , which are disfavoured by the most recent estimates obtained both through Cosmic Microwave Background and Inter-Galactic Medium observations .
Such bound weakens to f _ { PBH } M _ { PBH } \sim 170 ~ { } M _ { \odot } , when a conservative flat prior is instead assumed .
Both limits significantly improves previous constraints from the same physical observable .
We also extend our predictions to non-monochromatic PBH mass distributions , ruling out large regions of the parameter space for some of the most viable PBH extended mass functions .