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Narrow-line region gas kinematics of 24 264 optically selected AGN: The radio connection

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Abstract

Using a sample of 24 264 optically selected active galactic nuclei (AGNs) from the SDSSDR7 data base, we characterize how the profile of the [O III] λ5007 emission line relatesto bolometric luminosity (LAGN), Eddington ratio, radio loudness, radio luminosity (L1.4 GHz)and optical class (i.e. broad/narrow-line Seyfert 1, type 2) to determine what drives thekinematics of this kpc-scale line emitting gas. First, we use spectral stacking to characterizehow the average [O III] λ5007 profile changes as a function of these five variables. Afteraccounting for the known correlation between LAGN and L1.4 GHz, we report that L1.4 GHz hasthe strongest influence on the [OIII] λ5007 profile, with AGNs of moderate radio luminosity(L1.4 GHz = 1023-1025 WHz-1) having the broadest [OIII] λ5007 profiles. Conversely, we findonly a modest change in the [OIII] λ5007 profile with increasing radio loudness and find nosignificant difference between the [OIII] λ5007 profiles of broad-and narrow-line Seyfert 1s. When binned according to Eddington ratio, only the AGNs in our highest bin (i.e. >0.3) showany signs of having broadened [O III] λ5007 profiles, although the small numbers of suchextreme AGNs in our sample mean we cannot rule out that other processes (e.g. radio jets) areresponsible for this broadening. The [OIII] λ5007 profiles of type 1 and type 2 AGNs showthe same trends in terms of line width, but type 1 AGNs display a much stronger 'blue wing',which we interpret as evidence of outflowing ionized gas. We perform multicomponent fittingto the Hβ, [OIII] λλ4959, 5007, [N II] λλ6548, 6584 and Ha lines for all the AGNs in oursample to calculate the proportions of AGNs with broad [O III] λ5007 profiles. The individualfits confirm the results from our stacked spectra; AGNs with L1.4 GHz > 1023 WHz-1 areroughly five times more likely to have extremely broad [O III] λ5007 lines (full width at halfmaximum, FWHMAvg > 1000 km s-1) compared to lower L1.4 GHz AGNs, and the width ofthe [OIII] λ5007 line peaks in moderate-radio-luminosity AGNs (L1.4 GHz ~ 1024 WHz-1).Our results are consistent with the most disturbed gas kinematics being induced by compactradio cores (rather than powerful radio jets), although broadened [O III] λ5007 lines are alsopresent, but much rarer, in low-L1.4 GHz systems. Our catalogue of multicomponent fits is freelyavailable as an online resource for statistical studies of the kinematics and luminosities of thenarrow-and broad-line AGN regions and the identification of potential targets for follow-upobservations at http://sites.google.com/site/sdssalpaka. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

Publication metadata

Author(s): Mullaney JR, Alexander DM, Fine S, Goulding AD, Harrison CM, Hickox RC

Publication type: Article

Publication status: Published

Journal: Monthly Notices of the Royal Astronomical Society

Year: 2013

Volume: 433

Issue: 1

Pages: 622-638

Print publication date: 21/07/2013

Online publication date: 27/05/2013

ISSN (print): 0035-8711

ISSN (electronic): 1365-2966

Publisher: Oxford University Press

URL: https://doi.org/10.1093/mnras/stt751

DOI: 10.1093/mnras/stt751

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