What is it about? 🌠

Galaxies are constantly evolving, and stellar bars – radially elongated structures found at the centres of many disc galaxies (including our Milky Way!), are believed to play an important role in this evolution. But how these bars have changed over the history of the Universe remains poorly understood.  In this work, we have analyzed 600+ barred galaxies, spanning up to redshift 3 (corresponding to 11.7 billion years of cosmic history!) with the help of SDSS, the Hubble Space Telescope (HST) COSMOS, and the James Webb Space Telescope (JWST) CEERS surveys. In particular, we make a novel usage of dark gap (preferential light deficit along the bar minor axis) properties as a proxy for bar characteristics (strength and length).

Why is this work significant? 🔭

This represents one of the first systematic observational studies of galactic bar properties. Our results suggest that the formation of dark gaps is a fast mechanism and the initial rapid growth phase occurs well before z ~ 3. Thereafter it is followed by a mild growth phase, indicating bars are mostly stable features (at least in a statistical sense) – validating the earlier works in numerical simulation. Furthermore, we also show the dark gap strength to be another important parameter to characterize bars. 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 of galaxies at early cosmic times.