Tracing evolutionary pathways of bar-driven quenching in local Universe disc galaxies

TL;DR

This study investigates how bars influence star formation quenching in local disc galaxies, revealing an intermediate evolutionary stage characterized by residual star formation and older stellar populations in the central regions.

Contribution

It provides observational evidence for the role of bars in galaxy quenching, identifying a transitional phase with specific colour and age profiles in barred galaxies.

Findings

Discs are star-forming and bluer, while bulges and bars are redder with older stars.

A clear colour transition occurs at the bar end, indicating ongoing quenching.

Galaxies are in an intermediate stage before complete inner-region quenching.

Abstract

Bars play an integral role in regulating star formation (SF) in spiral galaxies, from triggering central starbursts to driving quenching. The diverse SF morphologies observed in local barred galaxies reflect different evolutionary stages of the bar, motivating studies across these stages. Here we study 12 nearby barred galaxies (z=0.01-0.06) identified as centrally quenched galaxies (having extended star-forming discs but quenched inner regions) by leveraging the differences in SFRs between the MPA-JHU and GSWLC catalogues. However, they exhibit residual central emission in the SDSS 3" fibre spectral region. Emission line analysis shows that this emission originates from either ongoing SF or LINER-like activity, suggesting diverse central ionization mechanisms. Using spatially resolved UV-optical colour maps from SDSS (r-band) and GALEX (FUV and NUV band) imaging data, we find that discs are star-forming and bluer in colour (NUV-r < 4 mag) while the bulge and bar regions are systematically redder (NUV-r > 4 mag) and dominated by older stellar populations. The NUV-r radial colour profiles show a clear transition from red to blue colours at the bar end with a corresponding median stellar age of ~ 1 Gyr. Compared to fully centrally quenched barred galaxies from our earlier work which lack SDSS fibre emission, these galaxies remain systematically bluer at similar radii, despite showing NUV-r > 4 mag inside the bar suggesting an intermediate stage in bar-driven quenching. We also estimate black hole masses associated with kinetic-mode AGN feedback and find them below the threshold (logM_BH < 8.0). Adding this with the presence of pseudo bulges, our results support bars as the primary drivers of quenching, with these galaxies representing an evolutionary phase just before their inner regions are completely quenched.