$H_0$ Tension on the Light of Supermassive Black Hole Shadows Data

Understand

Cosmological tensions in current times have opened a wide door to study new probes to constrain cosmological parameters, specifically, to determine the value of the Hubble constant $H_0$ through independent techniques.

• The two standard methods to measure/infer $H_0$ rely on: (i) anchored observables for the distance ladder, and (ii) establishing the relationship of the $H_0$ to the angular size of the sound horizon in the recombination era assuming a standard Cosmological Constant Cold Dark Matter ($\Lambda$CDM) cosmology.
• However, the former requires a calibration with observables at nearby distances, while the latter is not a direct measurement and is model-dependent.
• The physics behind these aspects restrains our possibilities in selecting a calibration method that can help minimise the systematic effects or in considering a fixed cosmological model background.