Searching for Dwarf H Alpha Emission-line Galaxies within Voids III: First Spectra

The presence or absence of dwarf galaxies with {M}_r^\prime > -14 in low-density voids is determined by the nature of dark matter halos. To better understand what this nature is, we are conducting an imaging survey through redshifted Hα filters to look for emission-line dwarf galaxies in the centers of two nearby galaxy voids called FN2 and FN8. Either finding such dwarfs or establishing that they are not present is a significant result. As an important step in establishing the robustness of the search technique, we have observed six candidates from the survey of FN8 with the Gillett Gemini telescope and GMOS spectrometer. All of these candidates had emission, although none was Hα. The emission in two objects was the [O III]λ4959, 5007 doublet plus Hβ, and the emission in the remaining four was the [O II]λ3727 doublet, all from objects beyond the void. While no objects were within the void, these spectra show that the survey is capable of finding emission-line dwarfs in the void centers that are as faint as {M}_r^\prime ∼ -12.4, should they be present. These spectra also show that redshifts estimated from our filtered images are accurate to several hundred km s^-1 if the line is identified correctly, encouraging further work in finding ways to conduct redshift surveys through imaging alone.