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

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 (0.02 ≲ z < 3) by making a novel usage 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 (Δμmax ) exhibits a weak evolution, increasing from higher redshifts (z ~ 2.5) and slightly declining towards lower redshifts (z < 0.05). Conversely, the extent of dark gaps (RDG, Rdark; normalised by bar length) decreases moderately from z ≥ 1.4 and remains constant thereafter. Our results suggest that bar formation and the initial rapid growth phase occur before z ~ 3, followed by mild growth towards lower redshifts. We also find Rdark to be a better proxy (as compared to RDG) for estimating bar length, supporting earlier theoretical studies. Furthermore, the Δμmax shows a weak but statistically significant correlation with bar-to-total light ratio (Bar/T) and bar ellipticity (εbar). 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.