Misclassified type 1 AGNs in the local universe

Abstract

We search for misclassified type 1 AGNs among type 2 AGNs identified with emission line flux ratios, and investigate the properties of the sample. Using 4\,113 local type 2 AGNs at $0.02<z<0.05$ selected from Sloan Digital Sky Survey Data Release 7, we detected a broad component of the \Ha\ line with a Full-Width at Half-Maximum (FWHM) ranging from 1\,700 to 19\,090 \kms\ for 142 objects, based on the spectral decomposition and visual inspection. The fraction of the misclassified type 1 AGNs among type 2 AGN sample is $\sim$3.5%, implying that a large number of missing type 1 AGN population may exist. The misclassified type 1 AGNs have relatively low luminosity with a mean broad \Ha\ luminosity, log L$_{H\alpha} = 40.50\pm0.35$ \ergs, while black hole mass of the sample is comparable to that of the local black hole population, with a mean black hole mass, log M$_{\rm BH} = 6.94\pm0.51$ M$_{\odot}$. The mean Eddington ratio of the sample is log L$_{\rm bol}$/L$_{\rm Edd}$ = $-2.00\pm0.40$, indicating that black hole activity is relatively weak, hence, AGN continuum is too weak to change the host galaxy color. We find that the \OIII\ lines show significant velocity offsets, presumably due to outflows in the narrow-line region, while the velocity offset of the narrow component of the \Ha\ line is not prominent, consistent with the ionized gas kinematics of general type 1 AGN population.