Cosmological test with the QSO Hubble diagram

Understand

A Hubble diagram (HD) has recently been constructed in the redshift range 0<z<6.5 using a non-linear relation between the ultraviolet and X-ray luminosities of QSOs.

• The Type Ia SN HD has already provided a high-precision test of cosmological models, but the fact that the QSO distribution extends well beyond the supernova range (z<1.8), in principle provides us with an important complementary diagnostic whose significantly greater leverage in z can impose tighter constraints on the distance versus redshift relationship.
• In this paper, we therefore perform an independent test of nine different cosmological models, among which six are expanding, while three are static.
• Many of these are disfavoured by other kinds of observations (including the aforementioned Type Ia SNe).