Abstract
One of the central questions in strong-gravity astrophysics is whether a surrounding dark matter distribution can create measurable imprints on black hole observables in the strong-field region. To explore this, we study a Schwarzschild black hole located in a Dehnen (1,4,5/2) dark matter halo using the self-consistent framework introduced by Bolokhov. We investigate how the halo parameters ( ρ s , r s ) modify the spacetime geometry and affect the motion of null and timelike particles near the black hole. Specifically, we focus on light paths related to the photon sphere, black hole shadow, lensing, transfer functions, and the grouping of direct, lensed, and photon-ring paths gathered through backward ray tracing. We further study thin accretion-disk observables within the Novikov–Thorne formalism, including the ISCO radius, radiative flux, temperature distribution, and differential luminosity. Finally, by confronting the predicted shadow size with the Event Horizon Telescope observations of Sgr A*, we place model dependent observational constraints on the allowed parameter space of the dark matter halo.