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 ($ρ= 0.96^{+0.03}_{-0.09}$; BF$_{10} > 100$) between the Bondi accretion power, $P_{\text{Bondi}}$, and the mechanical jet power, $P_{\text{jet}}$, for a subsample of 14 galaxies, which also host cool H$α$+[NII] 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 $\log \frac{P_{\mathrm{Bondi}}}{{10^{43} \, \mathrm{erg \, s^{-1}}}} = α+ β\log \frac{P_{\mathrm{jet}}}{{10^{43} \, \mathrm{erg \, s^{-1}}}}$, where $α= 1.10 \pm 0.25$ and $β= 1.10 \pm 0.24$ with an intrinsic scatter $σ= 0.08^{+0.14}_{-0.06}$ 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$α$+[NII] 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 ($M_{\bullet}$) and the specific entropy of the gas ($K$) at the Bondi radius. For the subsample of H$α$+[NII] emitting galaxies, we find a very tight correlation of $P_{\text{jet}}$ with $M_{\bullet}$ ($ρ= 0.91^{+0.06}_{-0.11}$; BF$_{10} > 100$) and, although poorly constrained, a hint of an anti-correlation for $P_{\text{jet}}$ and $K$ ($ρ= -0.47^{+0.60}_{-0.37}$; BF$_{10} = 1.1$).