A Direct Linkage Between AGN Outflows in The Narrow-line Regions and The X-ray Emission From The Accretion disks

TL;DR

This study finds a moderate correlation between [O III] line asymmetry and X-ray spectral steepness in AGNs, suggesting a link between outflows in the narrow-line region and accretion processes near the SMBH.

Contribution

It provides new evidence connecting AGN outflows in the NLR with the accretion activity, supporting wind/radiation models for outflow origins.

Findings

Stronger [O III] blue asymmetry correlates with steeper X-ray spectra.

The correlation is statistically significant at 2.78σ.

The accretion rate influences the outflow and spectral properties.

Abstract

The origin of outflow in narrow-line region (NLR) of active galactic nucleus (AGN) is studied in this paper by focusing on the relationship between the [\ion{O}{3}]$\lambda$5007 line profile and the hard X-ray (in a bandpass of 2-10 keV) emission from the central SMBH in type-I AGNs. A sample of 47 local X-ray selected type-I AGNs at $z<0.2$ is extracted from the 2XMMi/SDSS DR7 catalog that is originally crossmatched by Pineau et al. The X-ray luminosities in an energy band from 2 to 10keV of these luminous AGNs range from $10^{42}$ to $10^{44}\ \mathrm{erg\ s^{-1}}$. A joint spectral analysis is performed on their optical and X-ray spectra, in which the [\ion{O}{3}] line profile is modeled by a sum of several Gaussian functions to quantify its deviation from a pure Gaussian function. The statistics allows us to identify a moderate correlation with a significance level of 2.78$\sigma$: luminous AGNs with stronger [\ion{O}{3}] blue asymmetry tend to have steeper hard X-ray spectra. By identifying a role of $L/L_{\mathrm{Edd}}$ on the correlation at a $2-3\sigma$ significance level in both direct and indirect ways, we argue that the photon index versus asymmetry correlation provides evidence that the AGN's outflow commonly observed in its NLR is related with the accretion process occurring around the central SMBH, which favors the wind/radiation model for the origin of the outflow in luminous AGNs.