Relations of stellar mass between electron temperature-based metallicity of star-forming galaxies in a wide mass range

TL;DR

This study examines the relationship between stellar mass and metallicity in star-forming galaxies using electron temperature-based methods, revealing discrepancies with strong-line ratio methods and extending the mass range for such relations.

Contribution

It provides new stellar mass-metallicity relations for star-forming galaxies spanning from 10^6 to 10^{11} solar masses, based on direct electron temperature measurements.

Findings

Discrepancies between $T_e$-based and strong-line ratio metallicities increase with stellar mass.

Electron temperatures and ionic abundances vary depending on the analysis method used.

The sample galaxies tend to have lower metallicities and higher star formation rates.

Abstract

We select 947 star-forming galaxies from SDSS-DR7 with [O~{\sc iii}]$\lambda$4363 emission lines detected at a signal-to-noise {ratio }larger than 5$\sigma$. Their electron temperatures and direct oxygen abundances are {then }determined. {W}e compare the results from different methods. $t_2${, the} electron temperature in {the }low ionization region{,} estimated from $t_3${, that} in {the }high ionization region{,} {is} compared {using} three analysis relations between $t_2-t_3${. These} show obvious differences, which result in some different ionic oxygen abundances. The results of $t_3$, $t_2$, {$\rm O^{++}$/$\rm H^+$} and {$\rm O^{+}$/$\rm H^+$} derived by using methods from IRAF and literature are also compared. The ionic abundances $\rm O^{++}$/$\rm H^+$ {are} higher than $\rm O^{+}$/$\rm H^+$ for most cases. The{ different} oxygen abundances derived from $T_{\rm e}$ and the strong-line ratios show {a }clear discrepancy, which is more obvious following increasing stellar mass and strong-line ratio $R_{23}$. The sample{ of} galaxies from SDSS {with} detected [O~{\sc iii}]$\lambda$4363 have lower metallicites and higher {star formation rates}, {so} they may not be typical representatives of the whole{ population of} galaxies. Adopting data objects from {Andrews \& Martini}, {Liang et al.} and {Lee et al.} data, we derive new relations of stellar mass and metallicity for star-forming galaxies in a much wider stellar mass range: from $10^6\,M_\odot$ to $10^{11}\,M_\odot$.