Constraining Black Hole Parameters from Shadow and Inner-Shadow Morphology Considering Effects from Thick Disk Accretion Flows

TL;DR

This paper examines how emission geometry affects the ability to determine black hole parameters from shadow images, emphasizing the importance of accurate emission models and analyzing potential observations of M87* and Sgr A* with future telescopes.

Contribution

It demonstrates the necessity of assuming emission geometry for constraining black hole parameters from shadow measurements and evaluates observational prospects with upcoming observatories.

Findings

Shadow and inner-shadow radii can constrain black hole parameters if emission geometry and inclination are known.

Assuming the true emission geometry is crucial for accurate parameter estimation.

Future observations with BHEX and NgEHT can potentially constrain black hole properties under certain conditions.

Abstract

We study the effects of emission geometry on the capability to constrain black hole parameters from measurements of the shadow and inner-shadow of a Reissner-Nordstr\"om black hole. We investigate the capability to constrain mass, charge, observer inclination, and emission co-latitude from images of black hole accretion flows that would arise from thick and thin accretion disks. We confirm previous studies that have shown that independent radii measurements of the shadow and inner-shadow can constrain black hole parameters if the viewing inclination is known, but find that it is only possible if the true emission geometry is also assumed. We study the constraining capabilities of the shadow and inner-shadow observations of M87* and Sgr A* like systems within the context of the BHEX and NgEHT future observatories.