Cosmological constraints from the Hubble diagram of quasars at high redshifts

By G. Risaliti, E. Lusso. Nature Astronomy, 2018

280 citations recorded by the source corpus.

The concordance model (Λ cold dark matter (ΛCDM) model, where Λ is the cosmological constant) reproduces the main current cosmological observations1–4 assuming the validity of general relativity at all scales and epochs and the presence of CDM and of Λ, equivalent to dark energy with a constant density in space and time. However, the ΛCDM model is poorly tested in the redshift interval between the farthest observed type Ia supernovae5 and the cosmic microwave background. We present measurements of the expansion rate of the Universe based on a Hubble diagram of quasars. Quasars are the most luminous persistent sources in the Universe, observed up to redshifts of z ≈ 7.5 (refs. 6,7). We estimate their distances following a method developed by our group8–10, based on the X-ray and ultraviolet emission of the quasars. The distance modulus/redshift relation of quasars at z < 1.4 is in agreement with that of supernovae and with the concordance model. However, a deviation from the ΛCDM model emerges at higher redshift, with a statistical significance of ~4σ. If an evolution of the dark energy equation of state is allowed, the data suggest dark energy density increasing with time. The concordance cosmology model is poorly tested at high redshifts. Here the expansion rate of the Universe in the range 0.5 < z < 5.1 is measured based on a Hubble diagram of quasars, whose distances are estimated from their X-ray and ultraviolet emission.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/153fe5398ad7ca47ec05a291a055e994239a0710

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Citations in the corpus

On the Hubble Constant Tension in the SNe Ia Pantheon Sample (2021, background): “…H0 based on a combination of cosmological data, including calibration of the tip of the red giant branch on SNe Ia (Freedman et al. 2019), quasars (Risaliti & Lusso 2019), time-delay measurements, cosmic chronometers, and gamma-ray bursts (GRBs; Cardone et al. 2009, 2010; Dainotti et al. 2013b;…”
On the Evolution of the Hubble Constant with the SNe Ia Pantheon Sample and Baryon Acoustic Oscillations: A Feasibility Study for GRB-Cosmology in 2030 (2022, methodology): “Besides, there is a series of independent probes, such as quasars [49], the Tip of the Red-Giant Branch (TRGB) calibration through SNe Ia [50], and also GRBs [18,19,51–54], which bring estimates of H0 ranging between the values obtained with local measurements (SNe Ia and Cepheids) and Baryon Acoust”
A buyer’s guide to the Hubble constant (2021, unknown): “Quasars (Risaliti and Lusso 2019) and GRBs (Schaefer 2007) offer the prospect of extending the Hubble diagram up to z ∼ 5, further testing ΛCDM.”