The correlation between the 500 pc scale molecular gas masses and AGN powers for massive elliptical galaxies

Abstract

Abstract Massive molecular clouds have been discovered in massive elliptical galaxies at the center of galaxy clusters. Some of this cold gas is expected to flow in the central supermassive black holes and activate galactic nucleus (AGN) feedback. In this study, we analyze archival Atacama Large Millimeter Array (ALMA) data of nine massive elliptical galaxies, focusing on CO line emissions, to explore the circumnuclear gas. We show that the mass of the molecular gas within a fixed radius (500 pc) from the AGNs (Mmol ∼ 107–108 M⊙) is correlated with the jet power estimated from X-ray cavities (Pcav ∼ 1042–1045 erg s−1). The mass accretion rate of the circumnuclear gas $\dot{M}$ also has a correlation with Pcav. On the other hand, the continuum luminosities at ∼1.4 GHz and ∼100–300 GHz have no correlation with Mmol. These results indicate that the circumnuclear gas is sustaining the long-term AGN activities (∼107 yr) rather than the current ones. The circumnuclear gas mass is a better indicator of the jet power than the continuum luminosity, which probably changes on a shorter time scale. We also study the origin of the continuum emission from the AGNs at ∼100–300 GHz and find that it is mostly synchrotron radiation. For low-luminosity AGNs, however, dust emission appears to contaminate the continuum.