A Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE).X.
  Formation of a red ultra-diffuse galaxy and an almost dark galaxy during a
  ram-pressure stripping event
  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 $\sim$5 kpc from a UDG, namely NGVS 3543, in association with an HI gas
cloud AGC 226178, suggesting a recent interaction between this
low-surface-brightness system and the surrounding cluster environment. We use a
complete set of multi-frequency data including deep optical, UV, and
narrow-band H${\alpha}$ imaging and HI data to understand the formation process
that gave birth to this peculiar system. 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.
Comparisons of the observations with evolutionary models indicate that NGVS
3543 has undergone a ram-pressure stripping (RPS) that peaked $\sim$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
$\sim$10$^8$ M$_{\odot}$, forming star complexes with a typical age of $\sim$20
Myr and a stellar mass of $\sim$10$^4$ M$_{\odot}$. 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.
