the auroral lines, so-called ’strong-line’ diagnostics were developed based on the more easily measured nebular emission lines [@Pagel79; @Alloin79]. There have been many efforts to calibrate these diagnostics via theoretical [e.g., @McGaugh91; @Zaritsky94; @Dopita00; @Charlot01; @Kewley02; @Kobulnicky04; @Tremonti04; @Stasinska06] and empirical means [e.g., @Pilyugin03; @Pettini04; @Pilyugin05; @Pilyugin10; @Pilyugin12; @Marino13; @Bianco15].

Perhaps the most common of these diagnostics is ${\hbox{$R_{23}$}}~\equiv~(\text{[\ion{O}{ii}]}~\lambda 3727 + \text{[\ion{O}{iii}]}~\lambda\lambda 4959, 5007) / {\hbox{H$\beta$}}$ [@Edmunds84; @McCall85; @Dopita86; @Zaritsky94]. ${\hbox{$R_{23}$}}$ encodes some information about the overall oxygen abundance, but the ratio is ultimately determined by the excitation of the \[\] and \[\] lines. This leads to the double valued nature of ${\hbox{$R_{23}$}}$, which complicates its use as an abundance diagnostic.

Fortunately there are other nebular lines that encode information about the gas phase oxygen abundance, and nitrogen is the most accessible of these. Nitrogen has both primary origin, where the amount of nitrogen produced in stars and returned to the ISM is independent of metallicity, and secondary origin, where the amount of nitrogen produced is proportional to metallicity [@Alloin79; @Vila-Costa93; @Considere00]. In the high metallicity regime, nitrogen is secondary and the nitrogen abundance increases faster than the oxygen abundance. Furthermore, some strong line ratios are temperature sensitive since, for 