On type 1 active galactic nuclei with double-peaked [O~{\sc iii}]. I. data sample and basic results

TL;DR

This paper presents a systematic search for type 1 AGNs with double-peaked [O III] emission lines in SDSS data, resulting in a sample of 62 objects, and discusses possible models for the observed features.

Contribution

The study compiles the first large, systematically selected sample of 62 type 1 AGNs with double-peaked [O III], analyzing their properties and potential origins.

Findings

62 type 1 AGNs with double-peaked [O III] identified

Only 7 show signs of merging in imaging data

Velocity offsets suggest possible dual AGN nature

Abstract

Double-peaked narrow emission lines (DPNELs) might be evidence for the existence of kpc-scale dual AGNs. There are so far large samples of objects with DPNELs in narrow emission line galaxies. Here, a systematic search is made to build a sample of type 1 AGNs with double-peaked [O~{\sc~iii}] from Data Release 16 of the Sloan Digital Sky Survey (SDSS). Through visually inspecting and fitting [O~{\sc~iii}], fitting broad H$\alpha$ emission lines, performing F-test for [O~{\sc~iii}] profiles, and checking broad H$\beta$ and [O~{\sc~iii}] emission lines, we select 62 type 1 AGNs with reliable double-peaked [O~{\sc~iii}] from 11557 QSOs with z < 0.3. After visually checking the 62 SDSS multi-color images, we find only seven objects with signs of merging. Four possible models for the double-peaked [O~{\sc~iii}] observed in our sample are discussed: the superposition model, AGN outflow model, dual AGN model, and rotating disk model. However, the current results can not provide any one explanation conclusively, and additional observational data are needed to provide the details of narrow line regions. But at least 22 objects with different velocity offsets between double-peaked [O~{\sc~iii}] and narrow H$\alpha$ emission lines could be excluded as dual AGN candidates. The relative velocity offsets of the [O~{\sc~iii}] blue-shifted/red-shifted components are negative to their line flux ratios, which is consistent with dual AGN model. This work provides a new sample of 62 type 1 AGNs with double-peaked [O~{\sc~iii}] for further study.