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Special Colloquium |
Dr. Freek Roelofs
| SCHEDULED |
CFA
The Event Horizon Telescope (EHT) has imaged the black hole shadows of
the
supermassive black hole at the center of the galaxy M87 (M87*) and at
the
center of the Milky Way (Sgr A*). Polarimetric imaging of M87* with the
EHT
enabled significantly stronger inferences on the black hole and
accretion
parameters than total intensity data alone. Geometric modeling was a
central
tool for studying the structure of M87* and Sgr A* in total intensity.
In the
first part of the talk, I will show the results of fitting a new
polarimetric
“m-ring” geometric model to EHT observations of M87*. Our geometric
modeling
results are generally consistent with imaging methods, but they also
enable
studies of the black hole when imaging methods struggle, such as nights
with
sparse coverage or weak signals.
In the second part of the talk, I will focus on plans and science goals
for
future instruments. The Next-Generation EHT (ngEHT) will be a
transformative
enhancement of the EHT, with array expansions and improvements allowing
for,
e.g., high dynamic range imaging of AGN jets, and for real-time movie
reconstructions of variable sources like Sgr A*. With the ngEHT
Analysis
Challenges, we explore the science capabilities of the ngEHT, and
develop new
analysis algorithms capable of analyzing the large and complex ngEHT
datasets. Finally, I will give a brief overview of several proposals to
image
black holes using space-based telescopes, which achieve
order-of-magnitude
angular resolution improvements compared to what is attainable from the
ground and allow for high-precision tests of general relativity.