Polarization of Radiation Emitting From Around Spinning Black Holes

Palaoro, Alex, Astronomy, University of Virginia
Davis, Shane, AS-Astronomy (ASTR), University of Virginia

Black hole simulations have become increasingly relevant and necessary with the imaging from the Event Horizon Telescope of M87 and Sgr A* and polarization images from the Imaging X-ray Polarimetry Explorer. Building off of Athena++ modifications made by previous students, and the previous geokerr and ipole codes by Dexter & Agol (2009) and Moscibrodzka & Gammie (2018) respectively, the polarization results were examined closely and found to be erring. A re-implementation of the parallel transportation methods by Dexter (2016) showed the same polarization, meaning the original method wasn't wrong and there was some other error, likely in the initialization and interpretation of the black hole. Intensity was consistently correct across black holes, but the polarization fraction showed behaviour at higher energies that was inconsistent with what Schnittman & Krolik (2009) found, and inconsistent with theory. Polarization angle was less drastic in error, but could still be seen with anomalous behaviours at higher energies. It is likely the problem lies in how the Stokes vectors are being computed as their individual magnitudes aren't consistent with what they should be, and will need to be revisited, along with the initialization of the black hole problem since photon wave vectors mostly matched when implementing different methods. This thesis is submitted in partial completion of the requirements of the BS Astronomy-Physics Major.

BS (Bachelor of Science)
accretion, accretion discs, black hole physics, radiative transfer, relativistic processes
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