Polarized image of a rotating black hole surrounded by a cold dark matter halo Xin Qin, Songbai Chen, Zelin Zhang and Jiliang Jing Eur. Phys. J. C, 83 2 (2023) 159 Published online: 18 February 2023 DOI: 10.1140/epjc/s10052-023-11300-9