Shaving the Hair of Black Hole with Sagittarius A$^*$ from Event Horizon Telescope

Abstract: Recently, the Event Horizon Telescope collaboration has reported the first image of the supermassive black hole Sagittarius in the Galactic Center. We attempt to test the validity of the no-hair theorem of black holes using this new shadow observation. Considering the Einstein-Maxwell-klein-Gordon theory with a minimally-coupled scalar field, we find that our numerical result is consistent with the prediction of the no-hair theorem. However, we can not rule out the possibility that black holes with scalar hair may exist in some special cases.