  We study the possibility of identifying dark matter in the galactic center
from the physical properties of the electromagnetic radiation emitted from a
optical-thin disk region around a static and spherically symmetric black hole.
In particular, we consider two specific models for the optical-thin disk
region: a gas at rest and a gas in a radial free fall. Due to the effect of
dark matter on the spacetime geometry, we find that the dark matter can
increase or decrease the intensity of the electromagnetic flux radiation
depending on the dark matter model. To this end, we analyze two simple dark
matter models having different mass functions $\mathcal{M}(r)$, with a matter
mass $M$, thickness $\Delta r_s$ along with a dark matter core radius
surrounding the black hole. In addition to that, we explore the scenario of a
perfect fluid dark matter surrounding the black hole. We show that in order to
have significant effect of dark matter on the intensity of the electromagnetic
flux radiation, a high energy density of dark matter near the black hole is
needed. We also find that the surrounding dark matter distribution plays a key
role on the shadow radius and the intensity of the electromagnetic flux
radiation, respectively. Finally, we have used the relation between the shadow
radius and the quasinormal modes (QNMs) to compute the real part of QNM
frequencies.
