Galaxy And Mass Assembly (GAMA): The unimodal nature of the dwarf galaxy population

In this paper we aim to (i) test the number of statistically di stinct classes required to classify the local galaxy population, and, (ii) identify the differe nces in the physical and star formation properties of visually-distinct galaxies. To accomplish t his, we analyse the structural parame- ters (effective radius (Reff ), effective surface brightness within Reff (hµie), central surface brightness (µ0), and Sersic index (n)), obtained by fitting the light profile of 432 galaxies (0.002 < z 6 0.02; Viking Z-band), and their spectral energy distribution using multi -band photometry in 18 broadbands to obtain the stellar mass (M � ), the star formation rate (SFR), the specific SFR (sSFR) and the dust mass (Mdust), respectively. We show that visually distinct, star-forming dwarf galaxies (irregulars, blue spheroids and low surface brightness galaxies) form a unimodal population in a parameter space mapped by hµie, µ0, n, Reff , SFR, sSFR, M � , Mdust and (g − i). The SFR and sSFR distribution of passively evolving (dwarf) ellipticals on the other hand, s tatistically distinguish them from other galaxies with similar luminosity, while the giant gal axies clearly segregate into star- forming spirals and passive lenticulars. We therefore suggest that the morphology classifica- tion scheme(s) used in literature for dwarf galaxies only re flect the observational differences based on luminosity and surface brightness among the apparent distinct classes, rather than any physical differences between them.