Recalibration of [O ii] λ3727 as a Star Formation Rate Estimator for Active and Inactive Galaxies

• Published in: The Astrophysical journal Vol. 882; no. 2
• Main Authors: Zhuang, Ming-Yang, Ho, Luis C.
• Format: Journal Article
• Language: English
• Published: Philadelphia The American Astronomical Society 10.09.2019; IOP Publishing
• Subjects: Active galactic nuclei; Active galaxies; Astronomical models; Astrophysics; Emission analysis; Emission lines; Emissions; Galaxies; galaxies: abundances; galaxies: active; galaxies: ISM; galaxies: star formation; H alpha line; Metallicity; Photoionization; Radiation; Radiation pressure; Scattering; Star & galaxy formation; Star formation; Star formation rate; Stars; Stars & galaxies; Stellar mass
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/ab340d

We investigate the use of the [O ii] λ3727 emission line as a star formation rate (SFR) estimator using Sloan Digital Sky Spectra for nearly 100,000 star-forming galaxies and 5500 galaxies with narrow-line active galactic nuclei. Consistent with previous work, we find that the [O ii]/H ratio in star-forming galaxies depends strongly on gas-phase metallicity. Using metallicities derived from the [N ii] λ6584/[O ii] λ3727 method, we refine a metallicity-dependent SFR estimator based on [O ii] that is calibrated within a scatter of 0.056 dex against the more commonly used SFR indicator based on H emission. The scatter increases to only 0.12 dex if the metallicity is estimated using the stellar mass-metallicity relation. With the aim of extending the [O ii]-based SFR estimator to active galaxies, we calculate radiation pressure-dominated photoionization models to constrain the amount of [O ii] emission arising from the narrow-line region. We use the sample of active galaxies to demonstrate that the SFRs derived from [O ii], after accounting for nonstellar contamination, are consistent with independent SFR diagnostics estimated from the stellar continuum of the host galaxies.