Connecting the radio AGN life cycle to feedback: Ionised gas is more disturbed in young radio AGN

Abstract

In the host galaxies of radio AGN, kinematically disturbed gas due to jet-driven feedback is a widely observed phenomenon. Simulations predict that the impact of jets on the surrounding gas changes as they grow. Useful insights into this phenomenon can be obtained by characterising radio AGN into different evolutionary stages and studying their impact on gas kinematics. We present a systematic study of the [OIII] gas kinematics for a sample of 5720 radio AGN up to $z\sim0.8$ with a large 1.4 GHz luminosity range of $\approx10^{22.5}-10^{28}$W/Hz, and 1693 [OIII] detections. Taking advantage of the wide frequency coverage of LOFAR and VLA surveys from $144-3000$MHz, we determine the radio spectral shapes, using them to characterise sources into different stages of the radio AGN life cycle. We determine the [OIII] kinematics from SDSS spectra and link it to the life cycle. Our main conclusion is that the [OIII] gas is $\sim$3 times more likely to be disturbed in the peaked spectrum (PS) sources (that represent a young phase of activity) than non-peaked spectrum (NPS) sources (that represent more evolved sources) at $z<0.4$. This changes to a factor of $\sim$2 at $z>0.4$. This shows that on average, the strong impact of jets is limited to the initial stages of the radio AGN life cycle. At later stages, the impact on gas is more gentle. We also determine the dependence of this trend on 1.4GHz and [OIII] luminosities and find that the difference between the two groups increases with 1.4GHz luminosity. Young radio AGN with $L_\mathrm{1.4GHz}>10^{25}$W/Hz have the most extreme impact on [OIII]. Using a stacking analysis, we are further able to trace the changing impact on [OIII] in the high-frequency peaked spectrum (i.e. youngest), low-frequency peaked spectrum ("less young"), and non-peaked spectrum (evolved) radio AGN.