  In this paper, we consider the hypothesis that fractions of dark matter could
be constituted by primordial black holes (PBHs). To test this possibility, we
work out the observational properties of a static black hole embedded in the
dark matter envelope made of a PBH source. The corresponding modifications of
geometry due to such a physical system are investigated, with a particular
focus on the accretion disk luminosity in spiral galaxies. The impact of the
PBH presence is analyzed through modification of the disk luminosity and
kinematic quantities. Thus, we discuss possible constraints on the PBH
abundance in view of the most recent theoretical bounds. The results of our
study indicate that suitable PBH masses are
$M_\text{PBH}\in[10^6,10^{12}]M_\odot$ for PBH fractions
$f_\text{PBH}\in[10^{-3},1]$. In particular, a comparison with the predictions
of the exponential sphere density profile for dark matter suggests that the
best-matching configuration is achieved for $f_\text{PBH}=1$ and
$M_\text{PBH}=10^6 M_\odot$. Consequences with respect to the current knowledge
on primordial black hole physics are discussed.
