Evolution of bar-induced dark gaps in galaxy discs: evidence of strong bar-driven effects already at z > 2

Abstract

The properties of stellar bars play a crucial role in determining the bar-driven secular evolution in disc galaxies. However, a systematic observational study of the evolution of several bar properties (such as strength and length) across cosmic time is largely missing. In this paper, using a sample of 625 barred galaxies, taken from SDSS, HST COSMOS, and JWST CEERS surveys, we systematically investigate the evolution of bar properties over redshifts ((Formula presented) ) by making a novel use of dark gap (preferential light deficit along the bar minor axis) properties as a proxy for bar properties. We show that the dark gap strength ((Formula presented) ) exhibits a weak evolution, increasing from higher redshifts ((Formula presented) ) and slightly declining towards lower redshifts ((Formula presented) ). Conversely, the extent of dark gaps ((Formula presented)

normalized by bar length) decreases moderately from (Formula presented) and remains constant thereafter. Our results suggest that bar formation and the initial rapid growth phase occur before (Formula presented), followed by mild growth towards lower redshifts. We also find (Formula presented) to be a better proxy (as compared to (Formula presented) ) for estimating bar length, supporting earlier theoretical studies. Furthermore, the (Formula presented) shows a weak but statistically significant correlation with bar-to-total light ratio and bar ellipticity ((Formula presented) ). Studies of the redshift evolution of bar properties over such an extensive redshift range as done here are instrumental in constraining the bar-driven evolution at early cosmic times. © The Author(s) 2026. Published by Oxford University Press on behalf of Royal Astronomical Society. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.