Shadow and polarization images of rotating black holes in Kalb–Ramond gravity illuminated by several thick accretion disks

Abstract Using ray-tracing techniques, this paper investigates the optical and polarization images of rotating black holes in Kalb–Ramond (KR) gravity illuminated by thick accretion disks. We examine two accretion disk models: the phenomenological radiatively inefficient accretion flow (RIAF) model and the analytical ballistic approximation accretion flow (BAAF) model. The RIAF model incorporates both isotropic and anisotropic radiation. In all models, external bright rings corresponding to high-order images and an internal dark region associated with the event horizon are observed. At high observational inclinations, the inner shadow is obscured by radiation from the equatorial plane, which is significantly different from the thin accretion disk model. The primary distinction between isotropic and anisotropic radiation is that the latter causes distortion of the high-order image in the vertical direction, resulting in an elliptical structure. For the BAAF model, because certain regions become geometrically thinner under the conical approximation, the high-order images are narrower compared to those in the RIAF model. Furthermore, we find that an increase in the rotational parameter a leads to asymmetry in the intensity distribution of the high-order image, while an increase in the spontaneous Lorentz-violating parameters, $$\varsigma $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>ς</mml:mi> </mml:math> and $$\varpi $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>ϖ</mml:mi> </mml:math> , results in a decrease in the size of the high-order image. In the polarization image, linear polarization is found to be significantly influenced by the intensity, while it is relatively less affected by the parameters $$\varsigma $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>ς</mml:mi> </mml:math> and $$\varpi $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>ϖ</mml:mi> </mml:math> . The electric vector position angle is mainly affected by the parameters $$\varsigma $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>ς</mml:mi> </mml:math> and $$\varpi $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>ϖ</mml:mi> </mml:math> .