The Dawn Light of Blueberry Galaxies: Spectroscopic and Photometric
  Studies of two Starburst Dwarf Galaxies
  A population of so-called "blueberry" starbursting dwarf galaxies with
extremely blue colors, low-metallicities, and enormous ionization ratios, has
recently been found by Yang et al. (2017). Yet we still do not know their
detailed properties, such as morphologies, AGN occupations, massive star
contents, infrared emission, dust properties, etc. As a pilot study of the
blueberries, we investigate the spectroscopic and photometric properties of two
blueberry candidates, RGG B and RGG 5, for which Hubble Space Telescope
high-resolution images are available. We find that RGG B and RGG 5 perhaps are
likely to be two merging dwarf galaxy systems. RGG B may have a close merging
companion; yet the current evidence still cannot exclude the possibility that
RGG B is just disturbed by in-situ star formation through, e.g., outflows,
rather than undergoing a merger. RGG 5 presents stellar shells in the outskirt
which can be the powerful evidence of galaxy merging. We also find that, all of
the blueberries, including RGG B and RGG 5, are located close to the
theoretical maximum-starburst-line in the BPT diagram, have very high
ionization parameters, and relatively low hardness ionizing radiation fields,
exhibit nitrogen overabundances, and show extremely red mid-IR colors, and
reside in the so-called "ULIRGs/LINERs/Obscured AGN" region. The blueberry
galaxies may not harbor AGN.
