Destruction of Molecular Gas Reservoirs in Early-Type Galaxies by Active Galactic Nucleus Feedback

TL;DR

This study provides observational evidence that low-luminosity AGN episodes rapidly destroy molecular gas reservoirs in early-type galaxies, effectively suppressing residual star formation without the need for powerful quasar activity.

Contribution

It demonstrates a direct link between low-luminosity AGN activity and the rapid destruction of molecular gas in early-type galaxies, highlighting a different suppression mechanism from quasar-driven feedback.

Findings

Molecular gas disappears within 100 Myr of black hole accretion onset.

Low-luminosity AGN episodes are sufficient to suppress star formation.

The suppression mode differs from quasar-driven truncation during galaxy formation.

Abstract

Residual star formation at late times in early-type galaxies and their progenitors must be suppressed in order to explain the population of red, passively evolving systems we see today. Likewise, residual or newly accreted reservoirs of molecular gas that are fuelling star formation must be destroyed. This suppression of star formation in early-type galaxies is now commonly attributed to AGN feedback wherein the reservoir of gas is heated and expelled during a phase of accretion onto the central supermassive black hole. However, direct observational evidence for a link between the destruction of this molecular gas and an AGN phase has been missing so far. We present new mm-wavelength observations from the IRAM 30m telescope of a sample of low redshift SDSS early-type galaxies currently undergoing this process of quenching of late-time star formation. Our observations show that the disappearance of the molecular gas coincides within less than 100 Myr with the onset of accretion onto the black hole and is too rapid to be due to star formation alone. Since our sample galaxies are not associated to powerful quasar activity or radio jets, we conclude that low-luminosity AGN episodes are sufficient to suppress residual star formation in early-type galaxies. This `suppression mode' of AGN feedback is very different from the `truncation mode' linked to powerful quasar activity during early phases of galaxy formation.