Exploring millicharged dark matter components from the shadows

Abstract

Dark matter sectors with hidden interactions have been of much interest in recent years. These frameworks include models of millicharged particles as well as dark sector bound states, whose constituents have electromagnetic gauge interactions. These exotic, charged states could constitute a part of the total dark matter density. In this work, we explore in some detail the various effects, on the photon sphere and shadow of spherically symmetric black holes, due to dark matter plasmas furnished by such sectors. Estimating physically viable parameter spaces for the particle physics models and taking semi-realistic astrophysical scenarios that are amenable to theoretical analyses, we point out various modifications and characteristics that may be present. Many of these effects are unique and very distinct from analogous situations with conventional baryonic plasmas, or neutral perfect fluid dark matter surrounding black holes. While in many physically viable regions of the parameter space the effects on the near-horizon regions and black hole shadows are small, in many parts of the low particle mass regions the effects are significant, and potentially measurable by current and future telescopes. Such deviations, for instance, include characteristic changes in the photon sphere and black hole shadow radii, unique thresholds for the dark matter plasma dispersion where the photon sphere or black hole shadow vanishes, and where the dark matter plasma becomes opaque to electromagnetic waves. Alternatively, we point out that a non-observation of such deviations and characteristics, in future, could put constraints on interesting regions of the particle physics parameter space.

Horizon-scale tests of gravity theories and fundamental physics from the Event Horizon Telescope image of Sagittarius A ∗

“…The reason, as explained in [1121], is that the Kiselev metric does not describe a space-time surrounded by a perfect fluid in the sense we are using here: in fact, it is easy to show that the energy-momentum tensor sourcing the Kiselev metric inevitably possesses shear stress components, and therefore cannot describe a perfect fluid [1121]. This is not the case, instead, for the space-time described by equation (117), which has been explicitly derived by starting from a perfect fluid source term (see [1122][1123][1124][1125][1126][1127][1128][1129][1130][1131][1132][1133][1134][1135][1136][1137][1138][1139][1140][1141] for other relevant works).…”

Phenomenological implications on a hidden sector from the Festina Lente bound

“…• Other Bounds include Vacuum Biref., Accelerator cavities, Ortho-positronium, Lamb Shift, and Accelerators [22,23].…”

“…The thick dot-dashed cyan line is the Tremaine-Gunn (TG) bound which applies for fermions, and the dashed yellow line corresponds to the bosonic DM lower bound. In addition, we depict a compilation of bounds from red giants, white dwarfs, SN1987A, BBN, CMB, SLAC, WMAP, and DM relic abundance (Ω DM h 2 > 0.1) in different colors [18][19][20][21][22][23][24][25].…”