Alone on a wide wide sea. The origin of SECCO 1, an isolated
  star-forming gas cloud in the Virgo cluster
  SECCO1 is an extremely dark, low-mass (M_star=10^5 M_sun), star-forming
stellar system lying in the Low Velocity Cloud (LVC) substructure of the Virgo
cluster of galaxies, and hosting several HII regions. Here we review our
knowledge of this remarkable system, and present the results of (a) additional
analysis of our panoramic spectroscopic observations with MUSE, (b) the
combined analysis of Hubble Space Telescope and MUSE data, and (c) new
narrow-band observations obtained with OSIRIS@GTC to search for additional HII
regions in the surroundings of the system. We provide new evidence supporting
an age as young as 4 Myr for the stars that are currently ionising the gas in
SECCO1. We identify only one new promising candidate HII region possibly
associated with SECCO1, thus confirming the extreme isolation of the system. We
also identify three additional candidate pressure-supported dark clouds in
Virgo among the targets of the SECCO survey. Various possible hypotheses for
the nature and origin of SECCO1 are considered and discussed, also with the
help of dedicated hydrodynamical simulations showing that a hydrogen cloud with
the characteristics of SECCO1 can likely survive for >1 Gyr while traveling
within the LVC Intra Cluster Medium.
