Cosmological test using the high-redshift detection rate of FSRQs with the Square Kilometre Array

Abstract

We present a phenomenological method for predicting the number of flat-spectrum radio quasars (FSRQs) that should be detected by upcoming Square Kilometre Array (SKA) SKA1- MID Wide Band 1 and Medium-Deep Band 2 surveys. We use the Fermi blazar sequence and mass estimates of Fermi FSRQs, and γ -ray emitting narrow-line Seyfert 1 galaxies, to model the radio emission of FSRQs as a function of mass alone, assuming a near-Eddington accretion rate, which is suggested by current quasar surveys at z ≳ 6. This is used to determine the smallest visible black hole mass as a function of redshift in two competing cosmologies we compare in this paper: the standard δ cold dark matter (δCDM) model and the Rh = ct universe. We then apply lockstep growth to the observed black hole mass function at z = 6 in order to devolve that population to higher redshifts and determine the number of FSRQs detectable by the SKA surveys as a function of z. We find that at the redshifts for which this method is most valid, δCDM predicts ~30 times more FSRQs than Rh = ct for the Wide survey, and ~100 times more in the Medium-Deep survey. These stark differences will allow the SKA surveys to strongly differentiate between these two models, possibly rejecting one in comparison with the other at a high level of confidence.