Real-time cosmology with SKA

Yan Liu,Jing-Fei Zhang,Xin Zhang

doi:10.1140/epjc/s10052-020-7863-4

Yan Liu, Jing-Fei Zhang + Show 1 more

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https://doi.org/10.1140/epjc/s10052-020-7863-4

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Abstract

In this work, we investigate what role the redshift-drift data of the Square Kilometre Array (SKA) will play in the cosmological parameter estimation in the future. To test the constraint capability of the redshift-drift data of SKA-only, the Lambda CDM model is chosen as a reference model. We find that using the SKA1 mock data, the Lambda CDM model can be loosely constrained, while the model can be well constrained when the SKA2 mock data are used. When the mock data of SKA are combined with the data of the European Extremely Large Telescope (E-ELT), the constraints can be significantly improved, becoming almost as good as the data combination of the type Ia supernovae observation (SN), the cosmic microwave background observation (CMB), and the baryon acoustic oscillations observation (BAO). Furthermore, we explore the impact of the redshift-drift data of SKA on the basis of SN+CMB+BAO+E-ELT in the Lambda CDM model, the wCDM model, the CPL model, and the HDE model. We find that the redshift-drift measurement of SKA could help to significantly improve the constraints on dark energy and could break the degeneracy between the cosmological parameters. Therefore, we conclude that redshift-drift observation of SKA would provide a good improvement in the cosmological parameter estimation in the future and has the enormous potential to be one of the most competitive cosmological probes in constraining dark energy.

Highlights

Of dark energy, one should precisely measure the expansion history of the universe
Since the CDM model is widely regarded as a prototype of standard cosmology, we take this model as a reference model to test the constraining power of the Square Kilometre Array (SKA)-only mock data and make an analysis of constraints on cosmological parameters when the redshift-drift data of SKA and Extremely Large Telescope (E-ELT) are combined
The curve of v(z) is plotted according to Eq (23), with the fiducial values of parameters given by the best fit to the supernovae observation (SN)+cosmic microwave background observation (CMB)+baryon acoustic oscillations observation (BAO) data; the error bars on v, i.e., σ v, for each redshift bin, are plotted according to Eq (24) for E-ELT, and according to the detailed prescriptions described in the above section for SKA1 and SKA2

Summary

Introduction

Of dark energy, one should precisely measure the expansion history of the universe. Currently, the mainstream way is to measure the cosmic distances (luminosity distance or angular diameter distance) and the corresponding redshifts, and to establish a distance–redshift relation, by which constraints on the parameters of dark energy (and other cosmological parameters) can be made. The most typical real-time observable is the redshift drift, which can give a direct measurement for the expansion rate (namely, the Hubble parameter) of the universe in a specific range of redshift. The approach of measuring the redshift drift was first proposed by Sandage, who suggested a direct measurement of the redshift variation for the extra-galactic sources [1] At the time he wrote, obviously, such a measurement was out of reach with the technological limitation of the day. The method was further improved by Loeb, who suggested a more realistic way of measuring the redshift drift using Lyman-α absorption lines of the distant quasars (QSOs) to detect the redshift variation [2]. It has been shown that the redshift drift in the redshift range of 2 < z < 5 is rather useful to break the parameter degeneracies generated by other observations and can play an important role in the cosmological parameter estimation in the future

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