López-Corredoira, M.; Melia, F.; Lusso, E.; Risaliti, G.
Bibliographical reference
International Journal of Modern Physics D, Volume 25, Issue 5, id. 1650060
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3
2016
Citations
21
Refereed citations
19
Description
A Hubble diagram (HD) has recently been constructed in the redshift
range 0 ≲ z ≲ 6.5 using a nonlinear relation between the
ultraviolet (UV) and X-ray luminosities of quasi stellar objects (QSOs).
The Type Ia Supernovae (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
disfavored by other kinds of observations (including the aforementioned
Type Ia SNe). We wish to examine whether the QSO HD confirms or rejects
these earlier conclusions. We find that four of these models
(Einstein-de Sitter, the Milne universe, the static universe with simple
tired light and the static universe with plasma tired light) are
excluded at the > 99% C.L. The quasi-steady state model is excluded
at > 95% C.L. The remaining four models (ΛCDM/wCDM, the Rh =
ct universe, the Friedmann open universe and a static universe with a
linear Hubble law) all pass the test. However, only ΛCDM/wCDM and
Rh = ct also pass the Alcock-Paczyński (AP) test. The optimized
parameters in ΛCDM/wCDM are Ωm = 0.20‑0.20+0.24 and
wde = ‑1.2‑∞+1.6 (the dark energy equation-of-state).
Combined with the AP test, these values become Ωm =
0.38‑0.19+0.20 and wde = ‑0.28‑0.40+0.52. But whereas
this optimization of parameters in ΛCDM/wCDM creates some tension
with their concordance values, the Rh = ct universe has the advantage of
fitting the QSO and AP data without any free parameters.