Unveiling the origin of giant low surface brightness discs: results of
  the long-slit spectral observations
  Giant low surface brightness galaxies (gLSB) with radii of discs as large as
130 kpc challenge galaxy formation scenarios and it is still not well
understood how they form and evolve through the cosmic time. Here we present
analysis of deep long-slit spectroscopic observations of six gLSBs that we
obtained with the Russian 6-m telescope: UGC 1922, Malin 2, UGC 6614, UGC1382,
NGC 7589 and UGC 1378. We derived spatially resolved properties of stellar and
ionized gas kinematics and characteristics of stellar populations and
interstellar medium. The stars in the central regions are old and metal rich
for most of the galaxies. We revealed the presence of a kinematically decoupled
central component in the inner regions of UGC1922, UGC1382 and UGC6614, where
we detected counter-rotating kinematical components. We combine the results of
our observations with the results available in literature. There seems to be a
need for diversity of gLSBs formation scenarios: (i) some of them could have
formed by in-plane mergers of massive galaxies; (ii) for some others the major
merger scenario is excluded by our data. We revealed that most of gLSBs are
situated in low-density environment which possibly helped to preserve the giant
discs. At the same time at some point of the formation history of these systems
there should exist a reservoir of gas from which the massive discs were formed.
Future observations and detailed comparison with numerical simulations of
galaxy formation in the cosmological contest will help to clarify which gLSB
formation channel is more important.
