Measuring Photon Rings with the ngEHT
Published in Galaxies, 2022
Question
What constitutes a measurement of the photon ring?
Description
black holes can act as lenses, and will form infinite images of objects when vieweved upon. These images will often form multiple successive images, called photon rings, that will converge to a curve known as the critical curve. Plans to further increase the Event Horizon Telescipe’s (EHT) resolution through additional baselines into the Next Generation Event Horizon Telescope (ngEHT) may make it possible to measure a photon ring. It is thus important to define what is reasonable to be called measurement of the photon ring.
