Searching for Dwarf Hα Emission-line Galaxies within Voids. I. Survey Methods and First Observations

Abstract The population density of dwarf galaxies in low-density voids is likely determined by the dark matter halo mass function and how galaxy formation proceeds smaller halos. This depends on nature itself, making a tracer its properties. While dwarfs have been found smaller, closer voids, they proven difficult to find larger, more distant through magnitude-limited spectroscopic surveys. because these surveys detect an overwhelmingly large number objects behind that must be verified spectroscopically, void prohibitively inefficient expensive terms large-telescope time. Narrowband imaging for emission lines such as H α reduces background objects, although overall remains large. If done filter set with overlapping transmission wings, then object redshift can estimated from photometry alone. precision possible order magnitude greater than single-band photometry, caveat captured line identified other means. Broadband used reject enough unwanted type make obtaining spectra remaining feasible. In this study, we present survey M r ′ fainter −14 mag center 4.3 square degrees FN8. Using Sloan g ′ , r i exclude [O ii ] iii emitters follow-up only few dozen are required statistically estimate density.