GASP XIX: AGN and their outflows at the center of jellyfish galaxies
  The GASP survey, based on MUSE data, is unveiling the properties of the gas
in the so-called "jellyfish" galaxies: these are cluster galaxies with
spectacular evidence of gas stripping by ram pressure. In a previous paper, we
selected the seven GASP galaxies with the most extended tentacles of ionized
gas, and based on individual diagnostic diagrams concluded that at least five
of them present clear evidence for an Active Galactic Nucleus. Here we present
a more detailed analysis of the emission lines properties in these galaxies.
Our comparison of several emission line ratios with both AGN and shock models
show that photoionization by the AGN is the dominant ionization mechanism. This
conclusion is strengthened by the analysis of $\rm H\beta$ luminosities, the
presence of nuclear iron coronal lines and extended ($>10$ kpc) emission line
regions ionized by the AGN in some of these galaxies. From emission line
profiles, we find the presence of outflows in four galaxies, and derive mass
outflow rates, timescales and kinetic energy of the outflows.
