The relation between accretion rate and jet power in early-type galaxies with thermally unstable hot atmospheres

Abstract

We use Chandra X-ray data and Very Large Array radio observations for a sample of 20 nearby, massive, X-ray bright, early-type galaxies to investigate the relation between the Bondi accretion rates and the mechanical jet powers. We find a strong correlation (𝜌 = 0.96; BF 10 > 100) between the Bondi accretion power, 𝑃 Bondi , and mechanical jet power, 𝑃 jet , for a subsample of 14 galaxies, which also host cool H𝛼+[N ] line emitting gas and thus likely have thermally unstable atmospheres. The results indicate that in all galaxies with thermally unstable atmospheres the cooling atmospheric gas feeds the central black holes at a similar jet-to-Bondi power ratio. For five out of six galaxies with no signs of H𝛼+[N ] emission, however, the behaviour is different and the jet-to-Bondi power ratio is lower by 1-2 orders of magnitude. We also investigate the dependence of jet power on individual quantities in the Bondi formula such as the supermassive black hole mass (𝑀 • ) and the specific entropy of the gas (𝐾) at the Bondi radius. For the subsample of H𝛼+[N ] emitting galaxies, we find a very tight correlation of 𝑃 jet with 𝑀 • (𝜌 = 0.92; BF 10 > 100) and, although poorly constrained, a hint of an anti-correlation for 𝑃 jet and 𝐾 (𝜌 = −0.46; BF 10 = 1.2).