https://doi.org/10.1140/epjc/s10052-026-15827-5
Regular Article - Theoretical Physics
The impact of cold dark matter halo on black hole shadow and polarization images under thick disk illumination
1
College of Physics and Optoelectronic Engineering, Chongqing Normal University, 401331, Chongqing, People’s Republic of China
2
Department of Mechanics, Chongqing Jiaotong University, 400000, Chongqing, People’s Republic of China
3
Center for Gravitational Wave Experiment, National Microgravity Laboratory, Institute of Mechanics, Chinese Academy of Sciences, 100190, Beijing, People’s Republic of China
a
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Received:
15
March
2026
Accepted:
10
May
2026
Published online:
7
June
2026
Abstract
Using the ballistic approximation accretion flow model, this paper investigates the shadow and polarization images of a Kerr-like black hole surrounded by a cold dark matter halo. By numerically solving the geodesic and radiative transfer equations, we analyze the effects of the critical density 
, the scale radius of the dark matter halo 
, the spin parameter a, and the observer inclination 
on the resulting images. In all cases, a bright ring structure corresponding to higher-order images is observed, accompanied by an inner region of decreased intensity. The results show that both and increase the size of the higher-order images, while the spin parameter a and inclination modify the image morphology, producing a crescent-shaped bright region on the left side. In the polarization maps, the linear polarization degree 
is significantly lower in the higher-order image region, and the polarization vectors exhibit distinct distributions inside and outside the ring. Compared with the thin disk model, the thick disk model displays notable differences in both shadow and polarization images.
© The Author(s) 2026
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