Imaging and polarization patterns of various thick disks around Kerr-MOG black holes

TL;DR

This study models the imaging and polarization of thick accretion disks around Kerr-MOG black holes, demonstrating how deviations from general relativity affect observable features and proposing polarimetric imaging as a test for modified gravity.

Contribution

It introduces a detailed analysis of polarization patterns around Kerr-MOG black holes, highlighting the effects of the MOG parameter and accretion models on observable signatures.

Findings

Photon ring size increases with MOG parameter α.

Frame dragging causes brightness asymmetry.

Polarization features are sensitive to spin and α.

Abstract

We investigate the imaging and polarization properties of Kerr-MOG black holes surrounded by geometrically thick accretion flows. The MOG parameter $\alpha$ introduces deviations from the Kerr metric, providing a means to test modified gravity in the strong field regime. Two representative accretion models are considered: the phenomenological radiatively inefficient accretion flow (RIAF) and the analytical ballistic approximation accretion flow (BAAF). Using general relativistic radiative transfer, we compute synchrotron emission and polarization maps under different spins, MOG parameters, inclinations, and observing frequencies. In both models, the photon ring and central dark region expand with increasing $\alpha$, whereas frame dragging produces pronounced brightness asymmetry. The BAAF model predicts a narrower bright ring and distinct polarization morphology near the event horizon. By introducing the net polarization angle $\chi_{\text{net}}$ and the second Fourier mode $\angle\beta_2$, we quantify inclination- and frame-dragging-induced polarization features. Our results reveal that both $\alpha$ and spin significantly influence the near-horizon polarization patterns, suggesting that high-resolution polarimetric imaging could serve as a promising probe of modified gravity in the strong field regime.