  By exploiting the extreme environment of the black hole (BH) as a potential
place for axion-photon interaction, we use an axion-producing model of the
magnetized plasma to study the shadow of an asymptotically flat rotating BH
immersed into an axion-plasmon cloud. By aiming to reveal footprints of axion
in the dark shadow of BH, we in this paper explore the influence of the fixed
axion-plasmon background on the motion of incident photons around the rotating
BH. Under some free parameter settings, we find that axion-plasmon cloud around
rotating BH affects the shape and size of the shadow in such a way that its
role is distinguishable from non-magnetized plasma and standard vacuum
solutions. By being limited to high rotation BH, we show that the size of the
BH shadow increases as the axion-plasmon coupling gets strong. Interestingly,
our analysis indicates that as the mass of axion gets heavier, it can leave a
subtle imprint of itself on the shadow. Conversely, in the non-rotating limit
(Schwarzschild), by recovering the spherical symmetry of the shadow shape of
BH, its size decreases. In coordination with the trend of change in shadow
size, the investigation of the energy emission from the BH surrounded by the
magnetized plasma shows that the maximal energy emission rate from the rotating
BH in the presence of axion-plasmon cloud increases compared to the
non-magnetized plasma and the vacuum solutions. Subsequently, by relaxing the
rotation, the axion-plasmon cloud causes a decrease in the energy emission rate
from the BH.
