Shadows of black holes in dynamical Chern-Simons modified gravity

TL;DR

This paper investigates the shadow of slowly rotating black holes in dynamical Chern-Simons gravity, deriving shape predictions and comparing them with numerical methods to assess potential observational constraints.

Contribution

It extends previous studies by analytically deriving black hole shadow profiles in dynamical Chern-Simons gravity and comparing them with numerical ray tracing results.

Findings

Analytical shadow profiles agree with numerical ray tracing within approximations.

Forecasts potential constraints on Chern-Simons parameters using EHT data.

Provides a framework for testing modified gravity with black hole imaging.

Abstract

We revisit and extend the study of null geodesics around a slowly rotating black hole in Chern-Simons modified gravity. We employ the Hamilton-Jacobi formalism to derive the equations for the shadow profile and determine its shape. We compare our results with numerical ray tracing, finding good agreement within the validity of our approximations for slow rotation and small Chern-Simons coupling. We forecast constraints on the model parameters using the uncertainty in EHT data for the observed shadow of SgrA* as a reference.