  We use panoramic optical spectroscopy obtained with MUSE@VLT to investigate
the nature of five candidate extremely isolated low-mass star forming regions
(Blue Candidates, BCs hereafter) toward the Virgo cluster of galaxies. Four of
the five (BC1, BC3, BC4, BC5) are found to host several HII regions and to have
radial velocities fully compatible with being part of the Virgo cluster. All
the confirmed candidates have mean metallicity significantly in excess of that
expected from their stellar mass, indicating that they originated from gas
stripped from larger galaxies. In summary, these four candidates share the
properties of the prototype system SECCO 1, suggesting the possible emergence
of a new class of stellar systems, intimately linked to the complex duty cycle
of gas within clusters of galaxies. A thorough discussion on the nature and
evolution of these objects is presented in a companion paper, where the results
obtained here from MUSE data are complemented with Hubble Space Telescope
(optical) and Very Large Array (HI) observations.
