AGN-Driven Biconical Outflows as the Origin of the Double-Peaked [O~{\sc iii}] doublet in SDSS J134733.36+121724.27

TL;DR

This study re-examines SDSS J1347+1217 to resolve conflicting classifications and line profiles. By performing a detailed host galaxy subtraction using 39 simple stellar population templates plus a power-law AGN continuum, and applying multi-Gaussian fits to emission lines, the authors show that the [O III] doublet is best described by blue- and red-shifted components with an additional extended component, and that a broad Hα component is present while broad Hβ is not detected. An F-test compares models with and without an AGN continuum and broad Hα, strongly favoring a setup that includes a broad Hα and AGN continuum, and a corrected redshift of $z=0.121807$. Comparative analysis with earlier SP2 spectra confirms the broad Hα component, supporting a Type-1.9 AGN classification. The most plausible origin for the double-peaked [O III] lines is AGN-driven biconical outflows, rather than a dual AGN merger or a rotating NLR, although future observations are required to further strengthen these conclusions and map the outflow geometry.

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~{\sc iii}]$λ\lambda4959,5007$Å doublet and a broad H$α$. The former likely results from 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~{\sc iii}]$λ\lambda4959,5007$Å doublet is better described by two Gaussian components (blue-shifted and red-shifted) 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~{\sc 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.

Figures (5)

• Figure 1: The best descriptions of the host galaxy contributions in the SDSS spectrum of SDSS J1347+1217. In the top panel, in order to show clearer absorption features, the y-axis is plotted in logarithmic coordinates. The solid dark green line shows the SDSS spectrum, the solid blue line shows the SSP method-determined host galaxy contributions, the dashed blue line shows the determined AGN continuum emissions, and the solid red line shows the sum of the host galaxy contributions and the AGN continuum emissions. In the bottom panel, the line spectrum is shown as the SDSS spectrum minus the host galaxy contributions and the AGN continuum emissions.
• Figure 2: The best-fitting results and the corresponding residuals to the emission lines around H$\alpha$ (panels (a) and (b)), and around H$\beta$ (panels (c) and (d)), and the bad-fitting results and the corresponding residuals to the emission lines around H$\beta$ (panels (e) and (f)). In panels (a), (c), and (e), the solid dark green lines show the line spectrum, and the solid red lines show the best-fitting results. The horizontal dashed red line shows $f_\lambda = 0$. In panel (a), the solid and dashed blue lines show the determined core and extended components in narrow H$\alpha$, and the solid magenta line shows the determined component in broad H$\alpha$. The solid and dashed purple lines show the determined core and extended components in the [N ii] doublet. The solid and dashed cyan lines show the determined core and extended components in the [O i] doublet. The solid and dashed green lines show the determined core and extended components in the [S ii] doublet. In panel (c), the solid and dashed green lines show the determined core and extended components in narrow H$\beta$. The solid blue and red lines show the determined blue-shifted and red-shifted emission profiles in the [O iii] doublet. The dashed purple lines show the determined extended components in the [O iii] doublet. In panel (e), the solid blue line shows the determined core components in the [O iii] doublet. The other line styles have the same meanings as those in panel (c). In panels (b), (d), and (f), the corresponding residuals are shown in dark green, with the horizontal red lines showing residuals $= 0,\pm1$.
• Figure 3: The best-fitting results and the corresponding residuals to the emission lines around [O ii] (panels (a) and (b)) and around H$\gamma$ (panels (c) and (d)). In panels (a) and (c), the solid dark green lines show the line spectrum, and the solid red lines show the best-fitting results. In panel (a), the solid and dashed purple lines show the determined core and extended components in [O ii]$\lambda3727$Å. The solid and dashed cyan lines show the determined core and extended components in H$\epsilon$. The solid blue and red lines show the determined blue-shifted and red-shifted components in [Ne iii]. The dashed green line shows the determined extended component in [Ne iii]. In panel (c), the solid and dashed green lines show the determined core and extended components in H$\gamma$. The solid and dashed purple lines show the determined core and extended components in narrow H$\delta$. The solid blue and red lines show the determined blue-shifted and red-shifted emission profiles in [O iii]$\lambda4363$Å. The solid and dashed cyan lines show the determined core and extended components in [S ii]$\lambda4070$Å. In panels (b) and (d), the corresponding residuals are shown, with the horizontal red lines showing residuals $= 0,\pm1$.
• Figure 4: The best-fitting results and the corresponding residuals to H$\alpha$ and [N ii] emission lines for Model_a (panels (a) and (b)), Model_c (panels (c) and (d)), and Model_d (panels (e) with the y-axis shown on a logarithmic scale and (f)). All line styles have the same meanings as those in panels (a) and (b) in Fig. \ref{['line']}.
• Figure 5: Comparative analysis of the emission-line spectra of SDSS J1347+1217 between the SDSS and SP2 observations. The top left panel shows the best descriptions of the host galaxy contributions for the SP2 spectrum. The line styles have the same meanings as those in the top panel of Fig. \ref{['spec']}. The top right panel shows the comparison of the emission-line spectra after subtracting the host galaxy contributions and AGN continuum emissions between the SP2 (dark green) and SDSS (red; shifted upward by 80 along the y-axis for a clearer comparison). The middle panels show the detailed emission-line spectra within the top right panel between the SP2 (dark green) and SDSS (red) around H$\beta$ and H$\alpha$, respectively. The bottom panels show the spectral differences (SP2 - SDSS) around H$\beta$ and H$\alpha$, respectively. The horizontal solid red line shows $f_\lambda=0$. The red semi-transparent regions in the middle left and bottom left panels highlight the significant differences between the SP2 and SDSS spectra, which may be attributed to poor observational quality. The solid blue line in the bottom right panel indicates that a single Gaussian function provides a good description of the difference between the SP2 and SDSS spectra.