Active Galactic Nucleus-driven Biconical Outflows as the Origin of the Double-peaked [O <scp>iii</scp> ] Doublet in SDSS J134733.36+121724.27

Abstract In this manuscript, we recheck the spectroscopic properties of SDSS J134733.36+121724.27 (4C+12.50), confirming the presence of the double-peaked [O iii ] λλ 4959, 5007 Å doublet and a broad H α . The former likely results from active galactic nucleus (AGN)-driven biconical outflows, while the absence of a broad H β supports a classification of the source as a Type-1.9 AGN. We analyze its high-quality Sloan Digital Sky Survey (SDSS) optical spectrum after robustly subtracting host galaxy and AGN continuum contributions through a simple stellar population fitting method employing 39 templates and a power-law continuum. Each narrow line of the [O iii ] λλ 4959, 5007 Å doublet is better described by two Gaussian components (blueshifted and redshifted) than by a single Gaussian, as confirmed by the F-test. Broad components are included for both H α and H β , but only H α reveals a significant detection, further supported by a comparison between the SDSS spectrum and that previously reported. These results support that the object is highly consistent with a Type-1.9 AGN classification, and the double-peaked [O iii ] profiles are most likely produced by AGN-driven biconical outflows rather than by a rotating narrow-line region or a dual AGN merger system. Additional observations are still needed to strengthen these conclusions.