Measuring the evolution of stellar bars with the host galaxy's spin

TL;DR

This study investigates how stellar bars influence galaxy spin measurements and finds that weakly barred galaxies tend to be younger, more actively star-forming, and have higher spin proxies than strongly barred ones.

Contribution

It demonstrates the impact of bar formation on galaxy spin proxies and links bar strength to galaxy evolutionary stages using observational data.

Findings

Bar formation can decrease the mass-weighted spin proxy by up to 16%.

Weakly barred galaxies are statistically younger and more star-forming than strongly barred galaxies.

Weakly barred galaxies may be in a rapid formation phase, while strongly barred ones evolve more slowly.

Abstract

We examine to what extent the galaxy spin parameter proxy ($\lambda_R$) is affected by bar formation and how it is related to the strong and weak classifications of stellar bars. By creating mock observations of a simulated galaxy, we show that the emergence of a stellar bar can cause mass-weighted $\lambda_R$ to decrease by up to 16%, depending on the bar's orientation. This decrease can be exaggerated if there is a burst of star formation due to the bar driving gas to the center of the galaxy. We use the SAMI galaxy survey to show that weakly barred galaxies have statistically significant younger average stellar populations, higher galaxy spin proxy and higher specific star formation rates compared to strongly barred galaxies within one effective radius. If we consider galaxies with average light-weighted stellar population age less than 3 Gyr within one effective radius, we still find weakly barred galaxies to have a higher galaxy spin proxy than strongly barred galaxies. Based on these trends found from the SAMI galaxy survey, we suggest weakly barred galaxies are rapidly forming, similar to the bar formation process seen in simulations, while strongly barred galaxies are undergoing slower (secular) evolution.