The Scavenger Hunt for Quasar Samples to Be Used as Cosmological Tools

Abstract

Although the $\Lambda$ Cold Dark Matter model is the most accredited cosmological model, information at high redshifts ($z$) between type Ia supernovae ($z=2.26$) and the Cosmic Microwave Background ($z=1100$) is crucial to validate this model further. To this end, we have discovered a sample of 1132 quasars up to $z=7.54$ exhibiting a reduced intrinsic dispersion of the relation between ultraviolet and X-ray fluxes, ${\delta }_{\mathrm{F}}=0.22$ vs. ${\delta }_{\mathrm{F}}=0.29$ ($24\%$ less), than the original sample. This gold sample, once we correct the luminosities for selection biases and redshift evolution, enables us to determine the matter density parameter ${\Omega }_M$ with a precision of 0.09. Unprecedentedly, this quasar sample is the only one that, as a standalone cosmological probe, yields such tight constraints on ${\Omega }_M$ while being drawn from the same parent population of the initial sample.

Comments: 36 pages, 19 figures,2 table. Comments are welcome. Accepted in Galaxies