Shadow of Bonanno-Reuter Black Hole in Plasma Medium: Insights from EHT Sgr A* Observations

Abstract: We investigate the properties of black hole shadows in the renormalization group (RG) improved Bonanno-Reuter spacetime, incorporating quantum gravitational corrections via the scale-dependent parameter $(\tildeω)$ in a plasma medium. Light propagation in a non-uniform, pressureless plasma with a radial density profile is analyzed through modified equations of motion. The black hole shadow angular radius is computed, and its dependence on $\tildeω$ and the plasma index is analyzed. The analysis of specific limiting cases indicates systematic deviations of the black hole shadow relative to the classical Schwarzschild limit. Using Event Horizon Telescope (EHT) observations of Sgr~A*, we place constraints on $\tildeω$. Furthermore, within the considered parameter range, plasma and quantum-gravity effects exhibit an observational degeneracy, which future high-resolution measurements with the next-generation EHT are expected to break, thereby providing tighter constraints on the model parameters.