On Strong Correlation between Shifted Velocity and Line Width of Broad Blueshifted [O iii] Components in Quasars

Abstract

We report strong linear correlation between shifted velocity and line width of the broad blueshifted [O iii] components in Sloan Digital Sky Survey (SDSS) quasars. Broad blueshifted [O iii] components are commonly treated as indicators of outflows related to a central engine; however, it is still an open question whether the outflows are related to central accretion properties or related to local physical properties of narrow emission-line regions (NLRs). Here, the reported strong linear correlation with Spearman rank correlation coefficient 0.75 can be expected under the assumption of active galactic nuclei (AGNs) feedback-driven outflows, through a large sample of 535 SDSS quasars with reliable blueshifted broad [O iii] components. Moreover, there are very different detection rates for broad blueshifted and broad redshifted [O iii] components in quasars, and no positive correlation can be found between shifted velocity and line width of the broad redshifted [O iii] components, which provides further and strong evidence to reject the possibility of local outflows in NLRs leading to the broad blueshifted [O iii] components in quasars. Thus, the strong linear correlation can be treated as strong evidence for the broad blueshifted [O iii] components being better indicators of outflows related to central engine in AGNs. Furthermore, rather than central black hole masses, Eddington ratios and continuum luminosities have key roles in the properties of the broad blueshifted [O iii] components in quasars.

Are There Larger Stellar Velocity Dispersions in Low-redshift Type 1 AGNs than in Type 2 AGNs?

“…Similar to what we have recently done in Zhang (2021aZhang ( , 2021bZhang ( , 2021c, three broad Gaussian functions (second moment larger than 600 km s −2 ) are applied to describe the broad Hα, and seven narrow Gaussian components (second moment smaller than 600 km s −2 ) are applied to describe the narrow Hα, [O I], [N II], and [S II] doublets, and a power-law component is applied to describe continuum emissions underneath the broad Hα. Based on the measured parameters of the broad Hα using the Levenberg-Marquardt least-squares minimization technique, the following criteria are used to determine that there is no broad Hα: the three broad Gaussian components determined for the broad Hα with measured line fluxes and line widths two times smaller than the corresponding uncertainties, and the criteria used to determine that there are reliable broad Hα are that there is at least one broad Gaussian component with measured line flux and line width at least five times larger than their corresponding uncertainties and a second moment larger than 600 km s −1 .…”

“…The method above to measure stellar velocity dispersions through a single stellar template spectrum is not appropriate to determine host-galaxy contributions. More detailed descriptions of the SSP method can be found in Bruzual & Charlot (2003), Kauffmann et al (2003b), Cid Fernandes et al (2005), Cappellari (2017, and in our previous paper, Zhang (2014), Zhang & Feng (2016), Rakshit et al (2017), Zhang et al (2019), Zhang (2021Zhang ( , 2021aZhang ( , 2021b. Here, we do not show further detailed discussions on the SSP method any longer, but a simple description of the SSP method follows.…”

“…Therefore, simple descriptions are shown in the model functions to describe the emission lines around Hβ within the rest wavelength from 4400 to 5600 Å after subtracting the host-galaxy contributions. Similar to what we have recently done in Zhang (2021aZhang ( , 2021bZhang ( , 2021c, three broad Gaussian functions are applied to describe the broad Hβ, one narrow Gaussian component is applied to describe the narrow Hβ, two narrow and two broad Gaussian components are applied to describe the core and extended components of the [O III] λλ4959, Figure 1. Two examples of the best-fitting results (solid red line) to the absorption features around 4000 Å (solid dark green line) in the Type 1 AGN 0997-52734-0303 (PLATE-MJD-FIBERID) (top panels) and in the Type 2 AGN 0332-52367-0317 (bottom panels).…”

Dependence of Narrow-line Region Sizes on [O iii] Luminosity in Low-redshift Active Galactic Nuclei with Double-peaked Broad Balmer Emission Lines

“…Similar to what we have previously done in Zhang (2014), Zhang & Feng (2016), Zhang et al (2019), and Zhang (2021a, 2021b to describe the stellar lights included in SDSS spectra of BLAGN, we here exploit a power-law component α × λ β applied to describe the AGN continuum emissions and the 39 simple stellar population templates from Bruzual & Charlot (2003), which include a population age from 5 Myr to 12 Gyr, with three solar metallicities (Z = 0.008, 0.05, and 0.02). Then, through the Levenberg-Marquardt least-squares minimization method applied to the SDSS spectra with both narrow and broad emission lines being masked out, host-galaxy Note.…”

“…Besides, as shown in the residuals in Figure 1 and the best-fitting results and their corresponding residuals to emission lines around Hβ in Figure 2, it is not necessary to consider the optical Fe II emission lines in the 35 double-peaked BLAGN, besides the three double-peaked BLAGN SDSS 0966-52642-0499, SDSS 2123-53793-0443, and SDSS 2783-54524-0517. Similar to what we have undertaken in Zhang (2021a), model functions including optical Fe II templates (Kovacevic et al 2010) and probable He II component have been considered to describe the emissions within a rest wavelength from 4400 Å to 5600 Å in the line spectra of SDSS 0966-52642-0499, SDSS 2123-53793-0443, and SDSS 2783-54524-0517, of which the determined optical Fe II emissions are shown as dashed cyan lines in Figure 2. Last but not least, there are extended components in the narrow Balmer emission lines in the model functions; however, the extended narrow Balmer components are only detected in SDSS 0721-52228-0600.…”