Observations of dwarfs in nearby voids: implications for galaxy
  formation and evolution
  The intermediate results of the ongoing study of deep samples of ~200
galaxies residing in nearby voids, are presented. Their properties are probed
via optical spectroscopy, ugri surface photometry, and HI 21-cm line
measurements, with emphasis on their evolutionary status. We derive directly
the hydrogen mass M(HI), the ratio M(HI)/L_B and the evolutionary parameter
gas-phase O/H. Their luminosities and integrated colours are used to derive
stellar mass M(*) and the second evolutionary parameter -- gas mass-fraction
f_g. The colours of the outer parts, typically representative of the galaxy
oldest stellar population, are used to estimate the upper limits on time since
the beginning of the main SF episode. We compare properties of void galaxies
with those of the similar late-type galaxies in denser environments. Most of
void galaxies show smaller O/H for their luminosity, in average by ~30%,
indicating slower evolution. Besides, the fraction of ~10% of the whole void
sample or ~30% of the least luminous void LSB dwarfs show the oxygen deficiency
by a factor of 2--5. The majority of this group appear very gas-rich, with f_g
~(95-99)%, while their outer parts appear rather blue, indicating the time of
onset of the main star-formation episode of less than 1-4 Gyr. Such unevolved
LSBD galaxies appear not rare among the smallest void objects, but turned out
practically missed to date due to the strong observational selection effects.
Our results evidense for unusual evolutionary properties of the sizable
fraction of void galaxies, and thus, pose the task of better modelling of dwarf
galaxy formation and evolution in voids.
