[Submitted on 31 Oct 2022]
Abstract: We study a number of well-motivated theories of modified gravity with the
common overarching theme that they predict the existence of compact objects
such as black holes and wormholes endowed with scalar hair. We compute the
shadow radius of the resulting compact objects and demonstrate that black hole
images such as that of M87$^*$ or the more recent SgrA$^*$ by the Einstein
Horizon Telescope (EHT) collaboration may provide a powerful way to constrain
deviations of the metric functions from what is expected from general
relativity (GR) solutions. We focus our attention on
Einstein-scalar-Gauss-Bonnet (EsGB) theory with three well motivated couplings,
including the dilatonic and $Z_2$ symmetric cases. We then analyze the shadow
radius of black holes in the contest of the spontaneous scalarization scenario
within EsGB theory with an additional coupling to the Ricci scalar (EsRGB).
Finally, we turn our attention to spontaneous scalarization in the
Einstein-Maxwell-Scalar (EMS) theory and demonstrate the impact of the
parameters on the black hole shadow. Our results show that black hole imaging
is an important tool for constraining black holes with scalar hair and for some
part of the parameter space, black holes solutions with scalar hair may be
marginally favoured compared to solutions of GR.
Submission history
From: Georgios Antoniou [view email]
[v1]
Mon, 31 Oct 2022 17:49:14 UTC (1,604 KB)
