MUSE sneaks a peek at extreme ram-pressure stripping events - I. A kinematic study of the archetypal galaxy ESO137-001

We present Multi Unit Spectroscopic Explorer (MUSE) observations of ESO137-001, a spiral galaxy infalling towards the centre of themassive Norma cluster at z~0.0162. During the highvelocity encounter of ESO137-001 with the intracluster medium, a dramatic ram-pressure stripping event gives rise to an extended gaseous tail, traced by our MUSE observations to >30 kpc from the galaxy centre. By studying the Ha surface brightness and kinematics in tandem with the stellar velocity field, we conclude that ram pressure has completely removed the interstellar medium from the outer disc, while the primary tail is still fed by gas from the inner regions. Gravitational interactions do not appear to be a primary mechanism for gas removal. The stripped gas retains the imprint of the disc rotational velocity to ~20 kpc downstream, without a significant gradient along the tail, which suggests that ESO137-001 is fast moving along a radial orbit in the plane of the sky. Conversely, beyond ~20 kpc, a greater degree of turbulence is seen, with velocity dispersion up to ±100 km s-1. For a modeldependent infall velocity of vinf ~ 3000 km s-1, we conclude that the transition from laminar to turbulent flow in the tail occurs on time-scales =6.5 Myr. Our work demonstrates the terrific potential of MUSE for detailed studies of how ram-pressure stripping operates on small scales, providing a deep understanding of how galaxies interact with the dense plasma of the cluster environment.