A Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE)

<jats:p><jats:italic>Context.</jats:italic> The evolution of galaxies depends on their interaction with the surrounding environment. Ultra-diffuse galaxies (UDGs) have been found in large numbers in clusters. We detected a few star-forming blobs in the VESTIGE survey, located at ∼5 kpc from a UDG, namely NGVS 3543, in association with an HI gas cloud AGC 226178, suggesting a recent interaction between this low-surface-brightness system and the surrounding cluster environment.</jats:p> <jats:p><jats:italic>Aims.</jats:italic> We use a complete set of multi-frequency data including deep optical, UV, and narrow-band H<jats:italic>α</jats:italic> imaging and HI data to understand the formation process that gave birth to this peculiar system.</jats:p> <jats:p><jats:italic>Methods.</jats:italic> For this purpose, we measured (i) the multi-wavelength radial surface brightness profiles of NGVS 3543 and compared them to the predictions of spectro-photometric models of galaxy evolution in rich clusters; and (ii) the aperture photometry of the blue regions in the vicinity of NGVS 3543 in order to determine their age and stellar mass.</jats:p> <jats:p><jats:italic>Results.</jats:italic> Comparisons of the observations with evolutionary models indicate that NGVS 3543 has undergone a ram-pressure stripping that peaked ∼100 Myr ago, transforming a blue gas-rich UDG into a red gas-poor UDG. Star formation has taken place in the ram pressure stripped gas, the mass of which is ∼10<jats:sup>8</jats:sup> <jats:italic>M</jats:italic><jats:sub>⊙</jats:sub>, forming star complexes with a typical age of ∼20 Myr and a stellar mass of ∼10<jats:sup>4</jats:sup> <jats:italic>M</jats:italic><jats:sub>⊙</jats:sub>.</jats:p> <jats:p><jats:italic>Conclusions.</jats:italic> These results suggest that we are observing for the first time the ongoing transformation of a gas-rich UDG into a red and quiescent UDG under the effect of a ram-pressure stripping event. The same process could explain the lack of star-forming UDGs in rich environments observed in several nearby clusters.</jats:p>