Zusammenfassung
The Event Horizon Telescope (EHT) is a project to assemble a Very Long
Baseline Interferometry (VLBI) network of mm wavelength dishes that can resolve
strong field General Relativistic signatures near a supermassive black hole. As
planned, the EHT will include enough dishes to enable imaging of the predicted
black hole "shadow", a feature caused by severe light bending at the black hole
boundary. The center of M87, a giant elliptical galaxy, presents one of the
most interesting EHT targets as it exhibits a relativistic jet, offering the
additional possibility of studying jet genesis on Schwarzschild radius scales.
Fully relativistic models of the M87 jet that fit all existing observational
constraints now allow horizon-scale images to be generated. We perform
realistic VLBI simulations of M87 model images to examine detectability of the
black shadow with the EHT, focusing on a sequence of model images with a
changing jet mass load radius. When the jet is launched close to the black
hole, the shadow is clearly visible both at 230 and 345 GHz. The EHT array with
a resolution of 20-30\$\mu\$as resolution (\$\sim\$2-4 Schwarzschild radii) is able
to image this feature independent of any theoretical models and we show that
imaging methods used to process data from optical interferometers are
applicable and effective for EHT data sets. We demonstrate that the EHT is also
capable of tracing real-time structural changes on a few Schwarzschild radii
scales, such as those implicated by VHE flaring activity of M87. While
inclusion of ALMA in the EHT is critical for shadow imaging, generally the
array is robust against loss of a station.
Nutzer