Strong [OIII]{\lambda}5007 emission line compact galaxies in LAMOST DR9:
  Blueberries, Green Peas and Purple Grapes
  Green Pea and Blueberry galaxies are well-known for their compact size, low
mass, strong emission lines and analogs to high-z Ly{\alpha} emitting galaxies.
In this study, 1547 strong [OIII]{\lambda}5007 emission line compact galaxies
with 1694 spectra are selected from LAMOST DR9 at the redshift range from 0.0
to 0.59. According to the redshift distribution, these samples can be separated
into three groups: Blueberries, Green Peas and Purple Grapes. Optical
[MgII]{\lambda}2800 line feature, BPT diagram, multi-wavelength SED fitting,
MIR color, and MIR variability are deployed to identify 23 AGN candidates from
these samples, which are excluded for the following SFR discussions. We perform
the multi-wavelength SED fitting with GALEX UV and WISE MIR data. Color excess
from Balmer decrement shows these strong [OIII]{\lambda}5007 emission line
compact galaxies are not highly reddened. The stellar mass of the galaxies is
obtained by fitting LAMOST calibrated spectra with the emission lines masked.
We find that the SFR is increasing with the increase of redshift, while for the
sources within the same redshift bin, the SFR increases with mass with a
similar slope as the SFMS. These samples have a median metallicity of
12+log(O/H) of 8.10. The metallicity increases with mass, and all the sources
are below the mass-metallicity relation. The direct-derived Te-based
metallicity from the [OIII]{\lambda}4363 line agrees with the empirical
N2-based empirical gas-phase metallicity. Moreover, these compact strong
[OIII]{\lambda}5007 are mostly in a less dense environment.
