Beyond 31 mag/arcsec^2: the low surface brightness frontier with the
  largest optical telescopes
  The detection of optical surface brightness structures in the sky with
magnitudes fainter than 30 mag/arcsec^2 (3sigma in 10x10 arcsec boxes; r-band)
has remained elusive in current photometric deep surveys. Here we show how
present-day 10 meter class telescopes can provide broadband imaging 1.5-2 mag
deeper than most previous results within a reasonable amount of time (i.e. <10h
on source integration). In particular, we illustrate the ability of the 10.4 m
Gran Telescopio de Canarias (GTC) telescope to produce imaging with a limiting
surface brightness of 31.5 mag/arcsec^2 (3sigma in 10x10 arcsec boxes; r-band)
using 8.1 hours on source. We apply this power to explore the stellar halo of
the galaxy UGC00180, a galaxy analogous to M31 located at ~150 Mpc, by
obtaining a surface brightness radial profile down to mu_r~33 mag/arcsec^2.
This depth is similar to that obtained using star counts techniques of Local
Group galaxies, but is achieved at a distance where this technique is
unfeasible. We find that the mass of the stellar halo of this galaxy is ~4x10^9
Msun, i.e. 3+-1% of the total stellar mass of the whole system. This amount of
mass in the stellar halo is in agreement with current theoretical expectations
for galaxies of this kind.
