STUDYING ULTRA DIFFUSE GALAXIES IN VIRGO WITH CFHT-NGVS, GALEX-GUVICS AND CFHT-VESTIGE

International audienceIn the recent years, Ultra Diffuse Galaxies (UDGs) have been found in large numbers first in clusters (e.g. Koda et al. 2015), and then also in the field, with a very wide range of properties. The Virgo cluster being both nearby, and deeply observed at all wavelength, it is a prime target to search and study such galaxies in the cluster environment. It was not necessary the easier place to do so because of the large spatial extent of the galaxies due to its proximity. Recently, however, the Next Generation Virgo Survey (NGVS) (Ferrarese et al. 2012) has allowed us to characterize thousands of galaxies in Virgo, and to find more than 100 UDGs or LSB galaxies. After discussing some of the vague definitions of low/diffuse galaxies, this contribution presents some ongoing work concerning the study of such galaxies in Virgo, on the basis on the NGVS survey. We focus especially on the contribution of GALEX data in the UV and of the VESTIGE survey for the Hα emission. Finally, we show that simple models of galaxy evolution can allow us to test what can be the effect of ram-pressure stripping (by purely modifying the star formation history of galaxies that would be usual star forming galaxies if it was not the case). UDGs may be affected by a combination of effects but simple models allow us to study an effect that SHOULD be present in the cluster environment