A Systematic Search for Hidden Type 1 AGNs: Gas Kinematics and Scaling Relations

Abstract We search type 1 active galactic nuclei (AGNs) among emission-line galaxies, that are typically classified as type 2 AGNs based on emission line flux ratios if a broad component in the Hα line profile is not properly investigated. Using ∼24,000 type 2 AGNs at z < 0.1, initially selected from Sloan Digital Sky Survey Data Release 7 by Bae & Woo, we identify a sample of 611 type 1 AGNs based on the spectral fitting results and visual inspection. These hidden type 1 AGNs have relatively low luminosity with a mean broad Hα luminosity, log erg s−1 and low Eddington ratio with a mean log L bol/L Edd = −2.04 ± 0.34, while they do follow the black hole mass–stellar velocity dispersion relation defined by the inactive galaxies and the reverberation-mapped type 1 AGNs. We investigate ionized gas outflows based on the [ ] λ5007 kinematics, which show relatively high velocity dispersion and velocity shift, indicating that the line-of-sight velocity and velocity dispersion of the ionized gas in type 1 AGNs is, on average, larger than that of type 2 AGNs.