Metal Abundances of KISS Galaxies. VI. New Metallicity Relations for the KISS Sample of Star-forming Galaxies

We present updated metallicity relations for the spectral database of star-forming galaxies (SFGs) found in the KPNO International Spectroscopic Survey (KISS). New spectral observations of emission-line galaxies obtained from a variety of telescope facilities provide oxygen abundance information. A nearly fourfold increase in the number of KISS objects with robust metallicities relative to our previous analysis provides for an empirical abundance calibration to compute self-consistent metallicity estimates for all SFGs in the sample with adequate spectral data. In addition, a sophisticated spectral energy distribution fitting routine has provided robust calculations of stellar mass. With these new and/or improved galaxy characteristics, we have developed luminosity-metallicity (L-Z) relations, mass-metallicity (M*-Z) relations, and the so-called fundamental metallicity relation (FMR) for over 1450 galaxies from the KISS sample. This KISS M*-Z relation is presented for the first time and demonstrates markedly lower scatter than the KISS L-Z relation. We find that our relations agree reasonably well with previous publications, modulo modest offsets due to differences in the strong emission line metallicity calibrations used. We illustrate an important bias present in previous L-Z and M*-Z studies involving direct-method (Te) abundances that may result in systematically lower slopes in these relations. Our KISS FMR shows consistency with those found in the literature, albeit with a larger scatter. This is likely a consequence of the KISS sample being biased toward galaxies with high levels of activity.