Toward a direct measurement of the cosmic acceleration: roadmap and forecast on FAST

Abstract

HI absorption systems are great targets for direct measurement of the Sandage-Loeb (SL) effect throughout a wide range of redshift for ground-based radio telescopes. We demonstrate the significance of improving the accuracy of SL effect measurement in cosmological model selection. With its wide sky coverage and high sensitivity, we forecast that for 1 year of the upcoming commensal survey (CRAFTS) the FAST telescope is capable of discovering about 800 HI absorption systems thereby improving the SL measurement accuracy. Aiming to measurement the cosmic redshift drift rate at the precision of $\dot{z}\sim 10^{-10}\mathrm{decad}{\mathrm{e}}^{-1}$, we propose combined observation mode with blind-searching and targeted observation. For a decade of consecutive targeted spectroscopic observation with the frequency resolution at a level of sub-$0.1\mathrm{Hz}$, we could detect the first-order derivative of the cosmological redshift with the expected precision.

Accepted for publication in JCAP; 14 pages, 6 figures

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• The Five-Hundred-Meter Aperture Spherical Radio Telescope (FAST) Project
• Science with ASKAP - the Australian Square Kilometre Array Pathfinder
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• Toward a direct measurement of the cosmic acceleration: the first preparation with FAST
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• Quantifying effects of inhomogeneities and curvature on gravitational wave standard siren measurements of $H(z)$
• Probing galaxy evolution through HI 21-cm emission and absorption: current status and prospects with the Square Kilometre Array
• Unveiling the Universe with Emerging Cosmological Probes
• Toward a direct measurement of the cosmic acceleration: The pilot observation of H I 21cm absorption line at FAST
• The FAST HI 21-cm absorption blind survey. II. -- Statistic Exploration for Associated and Intervening systems
• Statistical distribution of HI 21cm intervening absorbers as potential cosmic acceleration probes
• Redshift drift effect through the observation of HI 21cm signal with SKA
• A first quantification of the effects of absorption for HI Intensity Mapping experiments
• Estimating constraints on cosmological parameters via the canonical and the differential redshift drift with SKA HI 21-cm observations
• FLRW Kinematic-Induced Measurement of the Hubble Constant from Cosmic Chronometer and Redshift Drift Observations
• Safely simplifying redshift drift computations in inhomogeneous cosmologies: Insights from LTB Swiss-cheese models