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Description
The interaction of galaxies with their environment plays an important role in their evolution. 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 ~5kpc from a UDG, namely NGVS 3543, in association with an HI gas cloud AGC 226178, suggesting a recent interaction of this low surface brightness system with the surrounding cluster environment. We use a complete set of multi-frequency data including deep optical, UV, and narrow- band H{alpha} imaging and HI data to understand the formation process which gave birth to this peculiar system. For this purpose, we measured: i) 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, ii) aperture photometry of the blue regions in the vicinity of NGVS 3543 in order to determine their age and stellar mass. The comparison of the observations with the evolutionary models indicate that the NGVS 3543 has undergone a ram-pressure stripping (RPS) that peaked ~100Myr ago, transforming a blue gas-rich UDG into a red gas-poor UDG. Star formation has taken place in the ram pressure stripped gas, whose mass is ~10^8^M_{sun}_, forming star complexes of typical age ~20Myr and stellar mass ~10^4^M_{sun}_. 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 thus explain the lack of star forming UDGs in rich environments observed in several nearby clusters.
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