Mon. Not. R. Astron. Soc., 473, 1956-1966 (2018)
J0811+4730: the most metal-poor star-forming dwarf galaxy known.
IZOTOV Y.I., THUAN T.X., GUSEVA N.G. and LISS S.E.
Abstract (from CDS):
We report the discovery of the most metal-poor dwarf star-forming galaxy (SFG) known to date, J0811+4730. This galaxy, at a redshift z = 0.04444, has a Sloan Digital Sky Survey (SDSS) g-band absolute magnitude Mg = -15.41 mag. It was selected by inspecting the spectroscopic data base in the Data Release 13 (DR13) of the SDSS. Large Binocular Telescope/Multi-Object Double spectrograph (LBT/MODS) spectroscopic observations reveal its oxygen abundance to be 12 + log O/H = 6.98 ± 0.02, the lowest ever observed for an SFG. J0811+4730 strongly deviates from the main sequence defined by SFGs in the emission line diagnostic diagrams and the metallicity-luminosity diagram. These differences are caused mainly by the extremely low oxygen abundance in J0811+4730, which is ∼10 times lower than that in main-sequence SFGs with similar luminosities. By fitting the spectral energy distributions of the SDSS and LBT spectra, we derive a stellar mass of M* = 106.24-106.29 M☉, and we find that a considerable fraction of the galaxy stellar mass was formed during the most recent burst of star formation.