Hα Dots: Direct-method Metal Abundances of Low-luminosity Star-forming Systems

Abstract

Utilizing low-luminosity star-forming systems discovered in the H α Dots survey, we present spectroscopic observations undertaken using the Kitt Peak National Observatory 4 m telescope for 26 sources. With determinations of robust, “direct”-method metal abundances, we examine the properties of these dwarf systems, exploring their utility in characterizing starburst galaxies at low luminosities and stellar masses. We find that the H α Dots survey provides an effective new avenue for identifying star-forming galaxies in these regimes. In addition, we examine abundance characteristics and metallicity scaling relations with these sources, highlighting a flattening of both the luminosity–metallicity ( L – Z ) and stellar mass–metallicity ( M * – Z ) relation slopes in these regimes as compared with those utilizing samples covering wider respective dynamic ranges. These local, accessible analogs to the kinds of star-forming dwarfs common at high redshift will help shed light on the building blocks that assembled into the massive galaxies common today.