reservoirs, and are often forming stars, or as dwarf spheroidals (dSphs, or dwarf ellipticals, dEs), which have regular isophotes, are gas-poor, and are not forming stars. BCDs are classified in a variety of ways, but are observationally remarkable for their strong emission lines and star formation [@sargentsearle70; @searlesargent72; @izotovthuan04], their underlying old stellar population [@loosethuan86; @aloisi07], their exceptionally low gas-phase metallicity [@terlevich91; @izotov94; @izotovthuan99; @hunter99], and their compact underlying stellar and HI distributions [@papaderos96; @vanzee98; @janowiecki14; @lelli14]. Some groups have hypothesized that a compact mass distribution is the most distinctive characteristic of a BCD [@vanzee98; @lelli14; @mcquinn15c].

Recently, many groups have used observations to study the evolutionary connections between BCDs and other dwarf galaxies. Detailed studies of individual extreme objects [e.g., @guseva01; @ashley14] and systematic surveys of many objects [e.g., @noeske07] have both suggested that BCDs are members of a rapidly evolving class of galaxies, and play an important role in dwarf galaxy evolution. Deep surface photometry studies [@noeske03; @noeske05] in addition to spectroscopic observations [@papaderos08] have highlighted the possible connections between BCDs and dwarf irregulars in terms of their structural parameters and chemical evolution. Other observations suggest that the unusually low metallicity of BCDs is more likely maintained by 