The Relationships between Active Galactic Nucleus Power and Molecular Gas Mass within 500 pc of the Center of Elliptical Galaxies

Abstract

The physical quantity that directly controls the feedback of active galactic nuclei (AGNs) in elliptical galaxies remains to be determined. The discovery of molecular gas around the AGNs suggests that the gas is fueling the AGNs. Therefore, we analyze Atacama Large Millimeter/submillimeter Array data for the CO line ( J = 1–0, 2–1, 3–2) emission and estimate the mass of molecular gas within 500 pc of the center of 12 noncentral elliptical galaxies (NCEGs) and 10 of the brightest cluster galaxies. We find that the mass ( M _mol ∼ 10 ^5 –10 ^9 M _☉ ) is correlated with the jet power of their AGNs, which is represented by ${P}_{\mathrm{cav}}\approx 4.1\times {10}^{42}{({M}_{\mathrm{mol}}/{10}^{7}\ {M}_{\odot })}^{1.3}\mathrm{erg}\ {{\rm{s}}}^{-1}$ , although NCEGs alone do not show the correlation. We also find that M _mol is correlated with the AGN continuum luminosities at ∼1.4 GHz ( L _1.4 ) and ∼100–300 GHz ( L _con ). Since P _cav reflects galactic-scale, long-term AGN activity, while the continuum luminosities reflect local (≲500 pc), short-term AGN activity, our results suggest that AGN activity depends on the amount of gas, regardless of its timescale. On the other hand, we cannot find a clear correlation between the mass of the black holes in the AGNs ( M _BH ) and P _cav . This suggests that M _mol , rather than M _BH , is the main factor controlling AGN activity. We confirm that the origin of the continuum emission from the AGNs at ∼1.4–300 GHz is mostly synchrotron radiation.

Keywords

• Elliptical galaxies
• Active galactic nuclei
• Jets
• Brightest cluster galaxies
• Interstellar medium