Q2122-444: a naked AGN fully dressed

TL;DR

This study reclassifies Q2122-444 as a typical type-1 AGN with broad emission lines, high accretion rate, and no significant obscuration, based on multiwavelength observations including X-ray, optical, and radio data.

Contribution

The paper provides new optical spectroscopic evidence that challenges previous classifications, revealing broad lines and clarifying the AGN's true nature.

Findings

Presence of broad Balmer lines contradicts previous type 2 classification.

Absence of radio emission rules out jet presence.

X-ray and UV data confirm high accretion rate and lack of intrinsic absorption.

Abstract

Based on previous spectral and temporal optical studies, Q2122-444 has been classified as a naked AGN or true type 2 AGN, that is, an AGN that genuinely lacks a broad line region (BLR). Its optical spectrum seemed to possess only narrow forbidden emission lines that are typical of type 2 (obscured) AGNs, but the long-term optical light curve, obtained from a monitoring campaign over more than two decades, showed strong variability, apparently ruling out the presence of heavy obscuration. Here, we present the results from a ~40 ks XMM-Newton observation of Q2122-444 carried out to shed light on the energetics of this enigmatic AGN. The X-ray analysis was complemented with ATCA radio data to assess the possible presence of a jet, and with new NTT/EFOSC2 optical spectroscopic data to verify the actual absence of a BLR. The higher-quality optical data revealed the presence of strong and broad Balmer lines that are at odds with the previous spectral classification of this AGN. The lack of detection of radio emission rules out the presence of a jet. The X-ray data combined with simultaneous UV observations carried out by the OM aboard XMM-Newton confirm that Q2122-444 is a typical type-1 AGN without any significant intrinsic absorption. New estimates of the black hole mass independently obtained from the broad Balmer lines and from a new scaling technique based on X-ray spectral data suggest that Q2122-444 is accreting at a relatively high rate in Eddington units.