Dark energy constraints from quasar observations

Abstract

Recent measurements of the parameters of the Concordance Cosmology Model (ΛCDM) done in the low-redshift Universe with Supernovae Ia/Cepheids, and in the distant Universe done with Cosmic Microwave Background (CMB) imply different values for the Hubble constant (67.4 ± 0.5 km s −1 Mpc −1 from Planck vs 74.03 ± 1.42 km s −1 Mpc −1 , Riess et al. 2019). This Hubble constant tension implies that either the systematic errors are underestimated, or the ΛCDM does not represent well the observed expansion of the Universe. Since quasars -active galactic nuclei -can be observed in the nearby Universe up to redshift z ∼ 7.5, they are suitable to estimate the cosmological properties in a large redshift range. Our group develops two methods based on the observations of quasars in the late Universe up to redshift z∼4.5, with the objective to determine the expansion rate of the Universe. These methods do not yet provide an independent measurement of the Hubble constant since they do not have firm absolute calibration but they allow to test the ΛCDM model, and so far no departures from this model were found.

Time Delay of MgII Emission Response for the Luminous Quasar HE 0435-4312: Towards Application of High-Accretor Radius-Luminosity Relation in Cosmology

“…The best fit in this case implies a slightly lower Ω m , but the contour error is large and covers the best fit from Planck Collaboration et al ( 2020) within 1σ confidence level. The data do not yet tightly constrain the cosmological parameters, but the MgII high-accretion subsample does not imply any departures from the standard model, and the data quality is much higher, and constraints better in comparison with the larger sample based on Hβ line and discussed in , and somewhat better than from the mixed sample discussed in Czerny et al (2020).…”

“…Another, more recent application of the RL relation is the possibility to utilize it for obtaining absolute monochromatic luminosities. From the measured flux densities, one can calculate luminosity distances and use them for constraining cosmological parameters (Haas et al 2011;Watson et al 2011;Czerny et al 2013a;Panda et al 2019;Czerny et al 2020). The problem for cosmological applications is that the RL relation exhibits a scatter, which has increased with the accumulation of more sources, especially including those with higher accretion rates (super-Eddington accreting massive black holes-SEAMBHs sample; Du et al 2015Du et al , 2018.…”

Past, present and Future of the Scaling Relations of Galaxies and Active Galactic Nuclei

“…L(FWHM) = L 0 • (FWHM) 4 1000 erg s −1 (40) where L 0 depends on the square of L/L Edd , the ionizing range of the spectral energy distribution, and a parameter directly derived from the UV spectra, the product density times ionization parameter that has been scaled to the typical value 10 9.6 cm −3 [898,899,892]. Until now, the FWHM of Hβ broad component and of AlIIIλ1860 have been adopted as VBEs [900,901,902]. Equation (40) implies that a simple measurement of the FWHM of a low-ionization line yields a z−independent estimate of the accretion luminosity [749, c.f.…”

“…The virial equation has been applied to xA quasars only (L/L Edd ∼ 1), although in principle could be useful for all quasars with known L/L Edd , provided a suitable emission line broadened by virial motions is used for the luminosity computation. At present, the virial equation can be considered for all xA quasars distributed over a wide range of luminosity and redshift, where conventional cosmological distance indicators are not available [906,901,902].…”