Deep optical imaging of the dark galaxy candidate AGESVC1 282
  The blind HI survey Arecibo Galaxy Environment Survey (AGES) detected several
unresolved sources in the Virgo cluster, which do not have optical counterparts
in the Sloan Digital Sky Survey. The origin of these dark clouds is unknown.
They might be crucial objects since they could be the so-called dark galaxies,
that is, the dark matter halos without stellar content that are expected from
cosmological simulations. In order to reveal the nature of the dark clouds, we
took a deep optical image of one them, AGESVC1 282, with the newly-commissioned
1.4m Milankovi\'c Telescope. After observing it for 10.4h in the $L$-filter,
the image reached a surface-brightness limit of about 29.1 mag arcsec$^{-2}$ in
$V$. No optical counterpart was detected. We placed an upper limit on the
$V$-band luminosity of the object of $1.1\times10^7\,L_\odot$, giving a stellar
mass below $1.4\times10^7\,M_\odot$ and a HI-to-stellar mass ratio above 3.1.
By inspecting archival HI observations of the surrounding region, we found that
none of the standard explanations for optically dark HI clouds fits the
available constraints on this object.
