GASP IV: A muse view of extreme ram-pressure stripping in the plane of
  the sky: the case of jellyfish galaxy JO204
  In the context of the GAs Stripping Phenomena in galaxies with Muse (GASP)
survey, we present the characterization of JO204, a jellyfish galaxy in A957, a
relatively low-mass cluster with $M=4.4 \times10^{14}M_\odot$. This galaxy
shows a tail of ionized gas that extends up to 30 kpc from the main body in the
opposite direction of the cluster center. No gas emission is detected in the
galaxy outer disk, suggesting that gas stripping is proceeding outside-in. The
stellar component is distributed as a regular disk galaxy; the stellar
kinematics shows a symmetric rotation curve with a maximum radial velocity of
200km/s out to 20 kpc from the galaxy center. The radial velocity of the gas
component in the central part of the disk follows the distribution of the
stellar component; the gas kinematics in the tail retains the rotation of the
galaxy disk, indicating that JO204 is moving at high speed in the intracluster
medium. Both the emission and radial velocity maps of the gas and stellar
components indicate ram-pressure as the most likely primary mechanism for gas
stripping, as expected given that JO204 is close to the cluster center and it
is likely at the first infall in the cluster. The spatially resolved star
formation history of JO204 provides evidence that the onset of ram-pressure
stripping occurred in the last 500 Myr, quenching the star formation activity
in the outer disk, where the gas has been already completely stripped. Our
conclusions are supported by a set of hydrodynamic simulations.
