VESTIGE XIX line spectra and RVs of NGC 4569 tail

The follow-up spectroscopic observations were made with APO/DIS, MMT/Binospec and CFHT/SITELLE. Besides the known 80kpc H{alpha} tail downstream of NGC 4569, the deep H{alpha} imaging data allow the H{alpha} tail detected to at least 230 kpc from the galaxy. More importantly, the H{alpha} clumps implied from the imaging data are confirmed with the spectroscopic data.

The H{alpha} clumps show a smooth radial velocity gradient across ~1300km/s, eventually reaching the velocity of the cluster. This discovery, for the first time, demonstrates the full deceleration process of the stripped ISM. This discovery also showcases the potential with wide-field H{alpha} survey on galaxy clusters to discover intracluster optical emission-line clouds originated from cluster galaxies.

These clouds provide kinematic tracers to the infall history of cluster galaxies and the turbulence in the ICM. They are also excellent multi-phase objects to study the classical cloud crushing problem and other relevant important physical processes.