HETDEX [OIII] Emitters I: A spectroscopically selected low-redshift
  population of low-mass, low-metallicity galaxies
  We assemble a sample of 17 low metallicity (7.45 < log(O/H)+12 < 8.12)
galaxies with z < 0.1 found spectroscopically, without photometric
pre-selection, in early data from the Hobby Eberly Telescope Dark Energy
Experiment (HETDEX). Star forming galaxies that occupy the lowest mass and
metallicity end of the mass-metallicity relation tend to be under sampled in
continuum-based surveys as their spectra are typically dominated by emission
from newly forming stars. We search for galaxies with high [OIII]$\lambda$5007
/ [OII]$\lambda$3727, implying highly ionized nebular emission often indicative
of low metallicity systems. With the Second Generation Low Resolution
Spectrograph on the Hobby Eberly Telescope we acquired follow-up spectra, with
higher resolution and broader wavelength coverage, of each low-metallicity
candidate in order to confirm the redshift, measure the H$\alpha$ and [NII]
line strengths and, in many cases, obtain deeper spectra of the blue lines. We
find our galaxies are consistent with the mass-metallicity relation of typical
low mass galaxies. However, galaxies in our sample tend to have similar
specific star formation rates (sSFRs) as the incredibly rare "blueberry"
galaxies found in (Yang et. al. 2017). We illustrate the power of spectroscopic
surveys for finding low mass and metallicity galaxies and reveal that we find a
sample of galaxies that are a hybrid between the properties of typical dwarf
galaxies and the more extreme blueberry galaxies.
