Measurements of the Hubble constant from combinations of supernovae and radio quasars

In this letter, we propose an improved cosmological model independent method of determining the value of the Hubble constant H₀. The method uses unanchored luminosity distances H₀d_L (z) from SN Ia Pantheon data combined with angular diameter distances d_A (z) from a sample of intermediate luminosity radio quasars calibrated as standard rulers. The distance duality relation between d_L (z) and d_A (z), which is robust and independent of any cosmological model, allows to disentangle H₀ from such combination. However, the number of redshift matched quasars and SN Ia pairs is small (37 data-points). Hence, we take an advantage from the Artificial Neural Network (ANN) method to recover the d_A (z) relation from a network trained on full 120 radio quasar sample. In this case, the result is unambiguously consistent with values of H₀ obtained from local probes by SH0ES and H0LiCOW collaborations. Three statistical summary measures: weighted mean H_∼0 = 73.51 (± 0.67) km s-¹ Mpc-¹ , median Med (H₀) = 74.71 (± 4.08) km s-¹ Mpc-¹ and MCMC simulated posterior distribution H₀ = 73.52_-0.68^+0.66 km s-¹ Mpc-¹ are fully consistent with each other and the precision reached 1% level. This is encouraging for the future applications of our method. Because individual measurements of H₀ are related to different redshifts spanning the range z = 0.5 - 2.0, we take advantage of this fact to check if there is any noticeable trend in H₀ measurements with redshift of objects used for this purpose. However, our result is that the data we used strongly support the lack of such systematic effects.