Oral Presentation
Imaging Black Hole Magnetic Fields with the Event Horizon Telescope
Presenter: Andrew Chael (Harvard University)
Images of the linear polarization of synchrotron radiation around AGN trace their projected magnetic field lines and provide key data for understanding the physics of accretion and jet formation near supermassive black holes. Observing at a wavelength of 1.3-mm, the Event Horizon Telescope (EHT) will be able to resolve structure on the scale of the Schwarzschild radius in the nearby supermassive black holes in Sgr A* and M87. Because VLBI incompletely samples the Fourier transform of the source image, any image reconstruction that fills in unmeasured spatial frequencies will not be unique and reconstruction algorithms are required. In this talk, I will introduce extensions of
the Maximum Entropy Method (MEM) for reconstructing linear polarimetric VLBI images. In contrast to previous work, our polarimetric MEM algorithm jointly images the Stokes parameters Q and U using only robust polarimetric ratios immune to atmospheric phase corruption. I will demonstrate this technique’s effectiveness in reconstructing images of M87’s magnetic field morphology from simulated EHT data. I will also discuss extensions of the MEM for producing images of Faraday rotation measure across an observing band, which will open a window on the magnetic field strength and plasma density at the M87 jet base.
asiaa.sinica.edu.tw