The ACCELERATION programme: I. Cosmology with the redshift drift

Abstract

Detecting the change of a cosmological object’s redshift due to the time evolution of the Universal expansion rate is an ambitious experiment that will be attempted with future telescope facilities. In this paper, we describe the ACCELERATION programme, which aims to study the properties of the most underdense regions of the Universe. One of the highlight goals of this programme is to prepare for the redshift drift measurement. Using the EAGLE cosmological hydrodynamic simulations, we estimate the peculiar acceleration of gas in galaxies and the Lyα forest. We find that star-forming ‘cold neutral gas’ exhibits large peculiar acceleration due to the high local density of baryons near star-forming regions. We conclude that absorption by cold neutral gas is unlikely to yield a detection of the cosmological redshift drift. On the other hand, we find that the peculiar accelerations of Lyα forest absorbers are more than an order of magnitude below the expected cosmological signal. We also highlight that the numerous low H i column density systems display lower peculiar acceleration. Finally, we propose a new ‘Lyα cell’ technique that applies a small correction to the wavelength calibration to secure a relative measurement of the cosmic drift between two unrelated cosmological sources at different redshifts. For suitable combinations of absorption lines, the cosmological signal can be more than doubled, while the affect of the observer peculiar acceleration is mitigated. Using current data of four suitable Lyα cells, we infer a limit on the cosmological redshift drift to be $\dot{v}_{\rm obs}\lt 65~{\rm m~s}^{-1}~{\rm yr}^{-1}$ (2σ).

Closing the cosmological loop with the redshift drift

“…This is a particularly pressing question since two other approaches to detecting the redshift drift have been recently proposed. The Cosmic Accelerometer 17 aims to lower the cost of the experiment, while the Acceleration Programme 18 proposes to measure the differential redshift drift between two non-zero redshifts, rather than measuring the drift with respect to today. In Ref.…”

Toward a direct measurement of the cosmic acceleration: the first preparation with FAST

“…Apart from these complex Doppler effects contributing to systematic bias, one also needs an accurate timing standard to establish the long-term frequency stability of the equipment over one decade. Time should be controlled better than cosmic acceleration with a few nanoseconds, ensuring the accuracy of channel labeling and the distribution of channel spacing (Cooke 2019).…”

“…Bolejko et al (2019) listed theoretical dynamical contaminations of redshift drift, suggested a method observing the drift of the subtraction of two redshifts within a negligible angular distance to reduce systematical errors, and combined redshift drift with the flux drift of the same origin to improve the availability of observation data. Through EAGLE cosmological hydrodynamic simulations, Cooke (2019) concluded that Lyman-α forest is a better probe of the acceleration, while cold HI cloud within the galaxy is easily affected by active components and hard to generate a detectable absorption.…”

The Instantaneous Redshift Difference of Gravitationally Lensed Images: Theory and Observational Prospects

“…However, such a direct detection would also provide a new cosmological probe for determining accelerating expansion (Uzan 2004(Uzan , 2007, constraining dark energy (Balbi & Quercellini 2007;Corasaniti et al 2007;Lake 2007;Zhang et al 2007), and measuring the possible temporo-spatial variation of cosmological parameters (Molaro et al 2005;Gordon et al 2007;Geng et al 2018;Amendola & Quartin 2021). In an extensive study, Liske et al (2008) demonstrated that the redshift drift will be observable using next-generation telescopes, such as the Extreme Large Telescope (ELT), through a 20-year campaign of monitoring absorption lines of hundreds of quasars (Liske et al 2008;Kim et al 2015;Cooke 2019;Melia 2022).…”