Sunday 16 March 2025
A team of astronomers has made a fascinating discovery about the role of bars in quenching star formation in galaxies. By studying the light emitted by stars and gas within these cosmic bodies, researchers have shed new light on how bars – long, narrow structures that run through the centre of galaxies – influence the birth and death of stars.
The study focused on a sample of 17 centrally quenched barred galaxies, which are galaxies whose central regions have stopped forming new stars. These galaxies were selected based on their position in the mass-star formation rate plane, and were found to be hosting pseudo-bulges rather than classical bulges. Pseudo-bulges are thought to form through the merger of disk galaxies, whereas classical bulges are formed through the collapse of a gas-rich cloud.
Using archival data from the Sloan Digital Sky Survey (SDSS) and the Galaxy Evolution Explorer (GALEX), scientists created spatially resolved colour maps of these galaxies. These maps allowed researchers to investigate the age and composition of stars within different regions of the galaxy. The results revealed that the inner regions of barred galaxies are significantly redder than their outer counterparts, indicating an older stellar population.
Furthermore, the study found that most of the galaxies in the sample host pseudo-bulges and do not harbour active galactic nuclei (AGN). AGN are incredibly luminous objects at the centres of some galaxies, powered by supermassive black holes. The absence of AGN suggests that the quenching of star formation in these galaxies is likely driven by secular processes within the galaxy itself, rather than through interactions with other galaxies.
Bars have long been thought to play a key role in the evolution of galaxies, driving the transfer of gas and stars from the outer regions towards the centre. This can lead to an increase in star formation rates, as well as the growth of supermassive black holes. However, this study highlights the importance of bars in quenching star formation in galaxies.
The findings suggest that bars may be responsible for funnelling gas towards the galactic centre, where it is consumed by stars or expelled from the galaxy altogether. This would effectively cut off the supply of fuel needed to sustain ongoing star formation, leading to a decline in the rate of new star birth.
This research has significant implications for our understanding of galaxy evolution and the role that bars play in shaping the properties of galaxies over cosmic time.
Cite this article: “Bars Quench Star Formation in Galaxies by Funneling Gas towards the Centre”, The Science Archive, 2025.
Galaxies, Star Formation, Quenching, Bars, Stellar Population, Pseudo-Bulges, Active Galactic Nuclei, Galaxy Evolution, Secular Processes, Sloan Digital Sky Survey
