Photometric AGN Selection Yields H0=71.76 km/s/Mpc in Joint SN Ia-QSO Hubble Diagram

The preprint constructs a joint Hubble diagram by anchoring SDSS DR14 quasars to calibrated SN Ia distances and applying a multivariate statistical-distance selection on redshift, magnitudes, and colors to isolate a representative AGN subsample. Posterior sampling returns median values H0 = 71.76 km s^{-1} Mpc^{-1} and Ωm = 0.294, placing the result between Planck and local Cepheid-SN Ia anchors. The selected quasars show no strong angular clustering and reproduce the reference distance-redshift relation with small scatter in multiple redshift intervals.

This approach addresses the Hubble tension by testing whether an empirically standardized AGN population can serve as an independent high-redshift rung. The selection criterion reduces the risk that Malmquist bias or color-dependent systematics dominate the inferred expansion rate. Because the method relies on photometric properties already available in wide-field surveys, it scales to upcoming datasets from LSST and Euclid without requiring new spectroscopy for every object.

Remaining limitations include the modest size of the current golden sample and the assumption that the X-ray–UV relation remains linear after selection. Larger, spectroscopically confirmed AGN samples and cross-checks against BAO or gravitational-lens time delays will be required to confirm whether the central value persists or shifts toward either existing tension pole.

Next steps involve extending the selection pipeline to eROSITA and DESI overlap regions and testing redshift-dependent evolution of the quasar relation with forthcoming X-ray and UV photometry.