A Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE).V.
  Properties of the ionised gas filament of M87
  We have observed the giant elliptical galaxy M87 during the Virgo
Environmental Survey Tracing Galaxy Evolution (VESTIGE), a blind narrow-band
Halpha+[NII] imaging survey of the Virgo cluster carried out with MegaCam at
the Canada French Hawaii Telescope (CFHT). The deep narrow-band image confirmed
the presence of a filament of ionised gas extending up to ~ 3 kpc in the
north-western direction and ~ 8 kpc to the south-east, with a couple of plumes
of ionised gas, the weakest of which, at ~ 18 kpc from the nucleus, was
previously unknown. The analysis of deep optical images taken from the NGVS
survey confirms that this gas filament is associated with dust seen in
absorption which is now detected up to ~ 2.4 kpc from the nucleus. We have also
analysed the physical and kinematical properties of the ionised gas filament
using deep IFU MUSE data covering the central 4.8 x 4.8 kpc^2 of the galaxy.
The spectroscopic data confirms a perturbed kinematics of the ionised gas, with
differences in velocity of ~ 700-800 km s^-1 on scales of < 1 kpc. The analysis
of 2D diagnostic diagrams and the observed relationship between the
shock-sensitive [OI]/Halpha line ratio and the velocity dispersion of the gas
suggest that the gas is shock-ionised.
