A Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE): V. Properties of the ionised gas filament of M 87

Abstract

We observed the giant elliptical galaxy M 87 during the Virgo Environmental Survey Tracing Galaxy Evolution (VESTIGE), a blind narrow-band Hα+[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 southeast, 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 also analysed the physical and kinematical properties of the ionised gas filament using deep IFU MUSE data covering the central 4.8×4.8 kpc2 of the galaxy. The spectroscopic data confirm 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]/Hα line ratio and the velocity dispersion of the gas suggest that the gas is shock-ionised.