Measurements of the Hubble constant and cosmic curvature with quasars: ultracompact radio structure and strong gravitational lensing

Author:

Qi Jing-Zhao1,Zhao Jia-Wei1,Cao Shuo2,Biesiada Marek3,Liu Yuting2

Affiliation:

1. Department of Physics, College of Sciences, Northeastern University, 110819 Shenyang, China

2. Department of Astronomy, Beijing Normal University, 100875 Beijing, China

3. National Centre for Nuclear Research, Pasteura 7, PL-02-093 Warsaw, Poland

Abstract

ABSTRACT Although the Hubble constant H0 and spatial curvature ΩK have been measured with very high precision, they still suffer from some tensions. In this paper, we propose an improved method to combine the observations of ultracompact structure in radio quasars and strong gravitational lensing with quasars acting as background sources to determine H0 and ΩK simultaneously. By applying the distance sum rule to the time-delay measurements of seven strong lensing systems and 120 intermediate-luminosity quasars calibrated as standard rulers, we obtain stringent constraints on the Hubble constant (H0 = 78.3 ± 2.9 km s−1 Mpc−1) and the cosmic curvature (ΩK = 0.49 ± 0.24). On the one hand, in the framework of a flat universe, the measured Hubble constant ($H_0=73.6^{+1.8}_{-1.6} \mathrm{\,km\,s^{-1}\,Mpc^{-1}}$) is strongly consistent with that derived from the local distance ladder, with a precision of 2 per cent. On the other hand, if we use the local H0 measurement as a prior, our results are marginally compatible with zero spatial curvature ($\Omega _K=0.23^{+0.15}_{-0.17}$) and there is no significant deviation from a flat universe. Finally, we also evaluate whether strongly lensed quasars would produce robust constraints on H0 and ΩK in the non-flat and flat Λ cold dark matter model, if the compact radio structure measurements are available from very long baseline interferometry observations.

Funder

National Natural Science Foundation of China

National Key Research and Development Program of China

CPC

Chinese Academy of Sciences

Beijing Normal University

Key Laboratory of Computational Astrophysics

Central Universities in China

Publisher

Oxford University Press (OUP)

Subject

Space and Planetary Science,Astronomy and Astrophysics

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