Stellar Systems in the direction of the Hickson Compact Group 44 - I.
  Low Surface Brightness Galaxies
  Context. In spite of the numerous studies of low-luminosity galaxies in
different environments, there is still no consensus about their formation
scenario. In particular, a large number of galaxies displaying extremely
low-surface brightnesses have been detected in the last year, and the nature of
these objects is under discussion. Aims. In this paper we report the detection
of two extended low-surface brightness (LSB) objects (mueff_g'~27 mag) found,
in projection, next to NGC 3193 and in the zone of the Hickson Compact Group
(HCG) 44, respectively. Methods. We analyzed deep, high-quality, GEMINI-GMOS
images with ELLIPSE within IRAF in order to obtain their brightness profiles
and structural parameters. We also search for the presence of globular clusters
(GC) in these fields. Results. We have found that, if these LSB galaxies were
at the distances of NGC 3193 and HCG 44, they would show sizes and luminosities
similar to those of the ultra-diffuse galaxies (UDGs) found in the Coma cluster
and other associations. In that case, their sizes would be rather larger than
those displayed by the Local Group dwarf spheroidal (dSph) galaxies. We have
detected a few unresolved sources in the sky zone occupied by these galaxies
showing colors and brightnesses typical of blue globular clusters. Conclusions.
From the comparison of the properties of the galaxies presented in this work,
with those of similar objects reported in the literature, we have found that
LSB galaxies display sizes covering a quite extended continous range (reff ~
0.3 - 4.5 kpc), in contrast to "normal" early-type galaxies, which shows reff ~
1.0 kpc with a low dispersion. This fact might be pointing to different
formation processes for both types of galaxies.
