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Recently, Active Galactic Nuclei (AGNs) have been proposed as standardizablecandles, thanks to an observed non-linear relation between their X-ray andoptical-ultraviolet (UV) luminosities, which provides an independentmeasurement of their distances. In this paper, we use these observables for thefirst time to estimate the parameters of f(R) gravity models (specifically theHu-Sawicki and the exponential models) together with the cosmologicalparameters. The importance of this type of modified gravity theories lies inthe fact that they can explain the late time accelerated expansion of theuniverse without the inclusion of a dark energy component. We have alsoincluded other observable data to the analyses such as estimates of the Hubbleparameter H(z) from Cosmic Chronometers, the Pantheon Type Ia supernovaecompilation, and Baryon Acoustic Oscillations measurements. Our results showthat the allowed space parameter is restricted when both AGN and BAO data areadded to CC and SnIa data, being the BAO data set the most restrictive one. Wecan also conclude that even though our results are consistent with the onesfrom the LCDM model, small deviations from General Relativity, than can besuccessfully described by the f(R) models studied in this paper, are alsoallowed by the considered data sets.

Testing f(R) gravity models with quasar X-ray and UV fluxes