Estimating constraints on cosmological parameters via the canonical and the differential redshift drift with SKA HI 21-cm observations

ABSTRACT Redshift drift effect, an observational probe that is independent of cosmological models, presents unique applications in specific cosmological epoch. By quantifying redshift drift signal, researchers can determine the rate of the Universe’s accelerated expansion and impose constraints on cosmological models and parameters. This study evaluates the precision in cosmological parameters estimation derived from this signal via HI 21cm signal, which is observed by the Square Kilometre Array (SKA) telescope, with spectral resolutions of 0.001 and 0.002 Hz over an observational period of $\Delta T = 0.5$ yr, utilizing two established techniques: the canonical redshift drift and the differential redshift drift method. The primary objective of this project is to ascertain the rate of cosmic acceleration and establish a solid foundation for real-time cosmology. The results reveal that both the methods impose highly precise constraints on cosmological parameters, with accuracy reaching the level of millimetre per second (mm s−1) or better. However, the canonical method provides relatively less stringent compared to the differential approach. Furthermore, when solely constraining the matter density parameter $\Omega _m$, the strategy can be adapted to the canonical method. None the less, the differential method exhibits clear advantages when simultaneously constraining the matter density parameter $\Omega _m$ and the equation of state of dark energy. These findings validate SKA’s capability in detecting redshift drift and refining observational cosmology and indicates that the effect can offer superior diagnostic capabilities compared to other techniques, provided that appropriate observational equipment or sufficient observational time is employed.