Properties of the KISS Green Pea Galaxies

Green Peas are a class of extreme star-forming galaxies at intermediate redshifts, originally discovered via color-selection using multi-filter, wide-field survey imaging data (Cardamone et al. 2009). They are commonly thought of as being analogs of high-redshift Ly$α$-emitting galaxies. The defining characteristic of Green Pea galaxies is a high-excitation nebular spectrum with very large equivalent width lines, leading to the recognition that Green Pea-like galaxies can also be identified in samples of emission-line galaxies. Here we compare the properties a sample of [O III]-selected star-forming galaxies (z = 0.29-0.41) from the KPNO International Spectroscopic Survey (KISS) with the color-selected Green Peas. We find that the KISS [O III]-selected galaxies overlap with the parameter space defined by the color-selected Green Peas; the two samples appear to be drawn from the same population of objects. We compare the KISS Green Peas with the full H$α$-selected KISS star-forming galaxy sample (z $<$ 0.1) and find that they are extreme systems. Many appear to be young systems at their observed look-back times (3-4 Gyr), with more than 90% of their rest-frame B-band luminosity coming from the starburst population. We compute the volume density of the KISSR Green Peas at z = 0.29-0.41 and find that they are extremely rare objects. We don't see galaxies as extreme as the KISSR Green Peas in the local Universe, although we recognize several lower-luminosity systems at z $<$ 0.1.