Probing multi-phase outflows and AGN feedback in compact radio galaxies:
  the case of PKSB 1934-63
  Young radio AGN are pivotal for our understanding of many of the
still-debated aspects of AGN feedback. In this paper we present a study of the
interstellar medium in the compact, peaked-spectrum radio galaxy PKSB1934-63
using X-shooter observations. Most of the warm ionized gas resides within a
circum-nuclear disk with a radius of about 200pc that is likely to constitute
the gas reservoir from which the central black hole feeds. On the other hand,
we find a biconical outflow of warm ionized gas with an estimated radius of
59+/-12pc. This matches the radial extent of the radio source and suggests that
the outflow is jet driven. Thanks to the superior wavelength coverage of the
data, we can estimate the density of the warm ionized gas using the
trans-auroral line technique, and we find that the outflowing gas has
remarkably high density, up to n_e~10^5.5cm^-3 . The estimated mass outflow
rate is low (M_dot=10^-3 - 10^-1 M_solar/yr) and the AGN feedback operates at
relatively low efficiency (E_dot/L_bol~10^-4 - 10^-3 %), in contrast to
predictions of theoretical models. In addition, optical and near-IR line ratios
show that the expansion of the radio source drives fast shocks (with velocities
v>500km/s) that ionize and accelerate the outflowing gas. At odds with the
properties of other compact, peaked-spectrum radio sources hosting warm ionized
gas outflows, we do not find signs of kinematically disturbed or outflowing gas
in phases colder than the warm ionized gas. We argue that this is due to the
young age of our source and thus to the recent nature of the AGN-ISM
interaction, and suggest that cold gas forms within the outflowing material and
the shock-ionized outflowing gas of PKSB1934-63 did not have enough time to
cool down, and accumulate in a colder phase. This scenario is also supported by
the multi-phase outflows of other compact and young radio sources in the
literature.
