Young radio jets breaking free: molecular and HI outflows in their centers

TL;DR

This paper reviews how young radio jets in AGN drive fast, massive outflows of HI and molecular gas, revealing jet-ISM interactions that influence galaxy evolution.

Contribution

It provides new observational evidence and numerical simulations showing the impact of radio jets on the surrounding gas in young AGN.

Findings

HI outflows are common in young radio AGN

Jets interact with a clumpy medium, driving outflows

Radio jets significantly affect molecular gas kinematics

Abstract

Our view of the central regions of AGN has been enriched by the discovery of fast and massive outflows of HI and molecular gas. Here we present a brief summary of results obtained for young (and restarted) radio AGN. We find that HI outflows tend to be particularly common in this group of objects. This supports the idea that the jet, expanding in a clumpy medium, plays a major role in driving these outflows. The clumpiness of the medium is confirmed by VLBI and ALMA observations. The HI observations reveal that, at least part of the gas, is distributed in clouds with sizes up to a few tens of pc and mass ~10^4 Msun. A change of the conditions in the outflow, with an increasing fraction of diffuse components, as the radio jets grow, is suggested by the high resolution HI observations. The molecular gas completes the picture, showing that the radio plasma jet can couple well with the ISM, strongly affecting the kinematics, but also the physical conditions of the molecular gas. This is confirmed by numerical simulations reproducing, to first order, the kinematics of the gas.