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

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 (rho = 0.96(-0.09)(+0.03); BF10 > 100) between the Bondi accretion power, P-Bondi, and the mechanical jet power, P-jet, for a subsample of 14 galaxies, which also host cool H alpha+[N II] line emitting gas and thus likely have thermally unstable atmospheres. The relation between the Bondi accretion power and the mechanical jet power for this subsample is well described by a power-law model log P-Bondi/10(43) erg s(-1) = alpha + beta log P-jet/10(43) erg s(-1), where alpha = 1.10 +/- 0.25 and beta = 1.10 +/- 0.24 with an intrinsic scatter sigma = 0.08(-0.06)(+0.14) dex. 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 the full sample of 20 galaxies, the correlation is weaker and in a subset of galaxies with no signs of H alpha+[N II] emission, we see a hint for a systematically lower jet-to-Bondi power ratio. We also investigate the dependence of jet power on individual quantities in the Bondi formula such as the supermassive black hole mass (M-center dot) and the specific entropy of the gas (K) at the Bondi radius. For the subsample of H alpha+[N II] emitting galaxies, we find a very tight correlation of P-jet with M-center dot (rho = 0.91(-0.11)(+0.06); BF10 > 100) and, although poorly constrained, a hint of an anticorrelation for P-jet and K (rho = -0.47(-0.37)(+0.60); BF10 = 1.1).