The impact of young radio jets traced by cold molecular gas
  Ranging from a few pc to hundreds of kpc in size, radio jets have, during
their evolution, an impact on their gaseous environment on a large range of
scales. While their effect on larger scales is well established, it is now
becoming clear that they can also strongly affect the interstellar medium (ISM)
inside the host galaxy. Particularly important is the initial phase ($<10^6$
yr) of the evolution of the radio jet, when they expand into the inner few kpc
of the host galaxy. Here we report on results obtained for a representative
group of young radio galaxies using the cold molecular gas as a tracer of
jet-ISM interactions. The sensitivity and high spatial resolution of ALMA and
NOEMA are ideal to study the details of this process. In many objects we find
massive molecular outflows driven by the plasma jet, even in low-power radio
sources. However, the observed outflows are limited to the circumnuclear
regions and only a small fraction of the ISM is leaving the galaxy. Beyond this
region, the impact of the jet seems to change. Fast outflows are replaced by a
milder expansion driven by the expanding cocoon created by the jet-ISM
interaction, resulting in dispersing and heating the ISM. These findings are in
line with predictions from simulations of jets interacting with a clumpy medium
and suggest a more complex view of the impact of AGN than presently implemented
in cosmological simulations.
