SDSS J092609.45+334304.1: a nearby unevolved galaxy
  We present the results of observations of the very low surface brightness
(VLSB) dwarf galaxy SDSS J092609.45+334304.1 with extreme parameters which
indicate its unevolved status. Namely, its value of O/H, derived as an average
of that in two adjacent HII regions at the NE edge of the disc, corresponds to
the parameter 12+log(O/H)=7.12+-0.02, which is amongst two lowest known. The
total HI flux measurement obtained with the Nancay Radio Telescope and the
photometric results imply that the galaxy ratio M(HI)/L_B ~3.0, is among the
top known in the Local Volume. The galaxy is situated in the region of a nearby
underdense region known as the Lynx-Cancer void, where other, unevolved
galaxies, including DDO 68, HS 0832+3542 and SAO 0822+3545, are known to be
present. The total mass of this almost edge-on VLSB galaxy is ~8.3 times larger
than its baryonic mass, implying the dynamical dominance of Dark Matter (DM)
halo. The (u-g), (g-r) colours of outer parts of this galaxy are consistent
with the ages of its main stellar population of 1--3 Gyr. Thanks to the galaxy
isolation, the small effect of current or recent star formation (SF), its
proximity and rather large HI flux (~2.5 Jy km/s), this VLSB dwarf is a good
laboratory for the detailed study of DM halo properties through HI kinematics
and the star formation processes in very metal-poor low surface density
environment. This finding, along with the discovery of other unusual dwarf
galaxies in this void, provides evidence for the relation between galaxy
evolution and its very low-density environment for the baryonic mass range of
10^{8} to 10^{9} Mo. This relation seems to be consistent with that expected in
the LambdaCDM models of galaxy and structure formation.
