Blueberry galaxies: the lowest mass young starbursts
  Searching for extreme emission line galaxies allows us to find low-mass
metal-poor galaxies that are good analogs of high redshift Ly$\alpha$ emitting
galaxies. These low-mass extreme emission line galaxies are also potential
Lyman-continuum leakers. Finding them at very low redshifts ($z\lesssim0.05$)
allows us to be sensitive to even lower stellar masses and metallicities. We
report on a sample of extreme emission line galaxies at $z\lesssim0.05$
(blueberry galaxies). We selected them from SDSS broadband images on the basis
of their broad band colors, and studied their properties with MMT spectroscopy.
From the whole SDSS DR12 photometric catalog, we found 51 photometric
candidates. We spectroscopically confirm 40 as blueberry galaxies. (An
additional 7 candidates are contaminants, and 4 remain without spectra.) These
blueberries are dwarf starburst galaxies with very small sizes ($<
1\hbox{kpc}$), and very high ionization ([OIII]/[OII]$\sim10-60$). They also
have some of the lowest stellar masses
($\log(\hbox{M}/\hbox{M}_{\odot})\sim6.5-7.5$) and lowest metallicities
($7.1<12+\log(\hbox{O/H})<7.8$) starburst galaxies. Thus they are small
counterparts to green peas and high redshift Ly$\alpha$ emitting galaxies.
