Würzburg 2018 – scientific programme
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GR: Fachverband Gravitation und Relativitätstheorie
GR 11: Black Holes
GR 11.2: Talk
Thursday, March 22, 2018, 14:20–14:40, NW-Bau - HS3
On the Present Ability to Test Theories of Gravity via Black-Hole Shadows — •Yosuke Mizuno1, Ziri Younsi1, Christian Fromm1, Oliver Porth1, Mariafelicia De Laurentis1, Hector Olivares1, Heino Falcke2, Michael Kramer3, and Luciano Rezzolla1 — 1Institut für Theoretische Physik, Goethe Universität, Frankfurt am Main, Germany — 2Department of Astrophysics/IMAPP, Radboud University Nijmegen, Nijmegen, The Netherlands — 3Max-Planck-Institut für Radioastronomie, Bonn, Germany
Upcoming sub-millimetre VLBI images of Sgr A* carried out by the Event-Horizon-Telescope Collaboration (EHTC) are expected to provide critical evidence for the existence of this supermassive black hole. In this work we assess our present ability to use EHTC images to determine if they correspond to a Kerr black hole as predicted by Einstein’s theory of general relativity or to a black hole in alternative theories of gravity. To this end, we perform GRMHD simulations and use GRRT calculations to generate synthetic shadow images of a magnetised accretion flow onto a Kerr black hole. In addition, and for the first time, we perform GRMHD simulations and GRRT calculations for a dilaton BH, which we take as a representative solution of an alternative theory of gravity. Taking into account the configuration of the VLBI observing array from the 2017 EHTC campaign, we find that it could be extremely difficult to distinguish between black holes from different theories of gravity, thus highlighting that great caution is needed when interpreting BH images as tests of general relativity.