Imaging the Supermassive Black Hole Shadow and Jet Base of M87 with the Event Horizon Telescope

Citation:

Ru-Sen Lu, Avery E. Broderick, Fabien Baron, John D. Monnier, Vincent L. Fish, Sheperd S. Doeleman, and Victor Pankratius. 2014. “Imaging the Supermassive Black Hole Shadow and Jet Base of M87 with the Event Horizon Telescope.” The Astrophysical Journal, 788.

Abstract:

The Event Horizon Telescope (EHT) is a project to assemble a Very LongBaseline Interferometry (VLBI) network of millimeter wavelength dishesthat can resolve strong field general relativistic signatures near asupermassive black hole. As planned, the EHT will include enough dishesto enable imaging of the predicted black hole "shadow," a feature causedby severe light bending at the black hole boundary. The center of M87, agiant elliptical galaxy, presents one of the most interesting EHTtargets as it exhibits a relativistic jet, offering the additionalpossibility of studying jet genesis on Schwarzschild radius scales.Fully relativistic models of the M87 jet that fit all existingobservational constraints now allow horizon-scale images to begenerated. We perform realistic VLBI simulations of M87 model images toexamine the detectability of the black shadow with the EHT, focusing ona sequence of model images with a changing jet mass load radius. Whenthe jet is launched close to the black hole, the shadow is clearlyvisible both at 230 and 345 GHz. The EHT array with a resolution of20-30 μas resolution (~2-4 Schwarzschild radii) is able to image thisfeature independent of any theoretical models and we show that imagingmethods used to process data from optical interferometers are applicableand effective for EHT data sets. We demonstrate that the EHT is alsocapable of tracing real-time structural changes on a few Schwarzschildradii scales, such as those implicated by very high-energy flaringactivity of M87. While inclusion of ALMA in the EHT is critical forshadow imaging, the array is generally robust against loss of a station.