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Register a new userDual AGN candidates with double-peaked [O III] lines matching that of confirmed dual AGNs
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We have performed a spectral decomposition to search for dual active galactic nuclei (DAGNs) in the Sloan Digital Sky Survey (SDSS) quasars with $z<0.25$. Potential DAGN candidates are searched by referencing velocity offsets and spectral shapes of double-peaked [O III] lines of known DAGNs. Out of 1271 SDSS quasars, we have identified 77 DAGN candidates. Optical and mid-infrared diagnostic diagrams are used to investigate the ionizing source in the DAGN candidates. The optical diagnostic analysis suggests 93% of them are powered by AGNs, and mid-infrared diagnostic analysis suggests 97% are powered by AGNs. About 1/3 of the SDSS images of the DAGN candidates show signs of tidal interaction, but we are unable to identify double nuclei in most of them due to the low spatial resolution of the archival imaging data available for most of the sample. The radio-loud fraction of the DAGN candidates ($sim$10%) is similar to that of typical AGNs.
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Double-peaked [O III]5007, profiles in active galactic nuclei (AGNs) may provide evidence for the existence of dual AGNs, but a good diagnostic for selecting them is currently lacking. Starting from $sim$ 7000 active galaxies in SDSS DR7, we assemble a sample of 87 type 2 AGNs with double-peaked [O III]5007, profiles. The nuclear obscuration in the type 2 AGNs allows us to determine redshifts of host galaxies through stellar absorption lines. We typically find that one peak is redshifted and another is blueshifted relative to the host galaxy. We find a strong correlation between the ratios of the shifts and the double peak fluxes. The correlation can be naturally explained by the Keplerian relation predicted by models of co-rotating dual AGNs. The current sample statistically favors that most of the [O III] double-peaked sources are dual AGNs and disfavors other explanations, such as rotating disk and outflows. These dual AGNs have a separation distance at $sim 1$ kpc scale, showing an intermediate phase of merging systems. The appearance of dual AGNs is about $sim 10^{-2}$, impacting on the current observational deficit of binary supermassive black holes with a probability of $sim 10^{-4}$ (Boroson & Lauer).
In this work, we report a radio galaxy with precessing jets, double-peaked emission lines and the presence of two compact radio components with a projected separation of ~6 parsec in Very Long Baseline Interferometry (VLBI) observations. The emission line peak separations could be suggesting the presence of a supermassive black hole binary (BBH) with a separation of 6.3 parsec, matching the VLBI results. The kinematic jet precession model applied to the jets of J1328+2751 indicates that if it is a BBH, the accretion disk of the primary black hole is not coplanar with the binary system orbit, making its jet precess under the effect of the torque produced by the secondary black hole. However, we find that the Bardeen-Petterson effect can also provide precession timescales compatible with the jet precession period inferred in this source. This source has previously been identified as a restarted double-double radio galaxy (DDRG). Our findings therefore have important ramifications for the nature of DDRGs in general.
We report on the torus constraints of the Compton-thick AGN with double-peaked optical narrow line region (NLR) emission lines, ANEPD-CXO245, at z=0.449 in the AKARI NEP Deep Field. The unique infrared data on this field, including those from the nine-band photometry over 2-24 $mu$m with the AKARI Infrared Camera (IRC), and the X-ray spectrum from Chandra allow us to constrain torus parameters such as the torus optical depth, X-ray absorbing column, torus angular width ($sigma$) and viewing angle ($i$). We analyze the X-ray spectrum as well as the UV-optical-infrared spectral energy distribution (UOI-SED) with clumpy torus models in X-ray (XCLUMPY; Tanimoto et al. 2019) and infrared (CLUMPY; Nenkova et al. 2008) respectively. From our current data, the constraints on $sigma$--$i$ from both X-rays and UOI show that the line of sight crosses the torus as expected for a type 2 AGN. We obtain a small X-ray scattering fraction (<0.1%), which suggests narrow torus openings, giving preference to the bi-polar outflow picture of the double-peaked profile. Comparing the optical depth of the torus from the UOI-SED and the absorbing column density $N_{rm H}$ from the X-ray spectrum, we find that the gas-to-dust ratio is $gtrsim 4$ times larger than the Galactic value.
The merging of supermassive black holes (SMBHs) is a direct consequence of our hierarchical picture of galaxy evolution. It is difficult to track the merging process of SMBHs during mergers of galaxies as SMBHs are naturally difficult to observe. We want to characterise and confirm the presence of two independent active galactic nuclei (AGN) separated by a few kiloparsec in seven strongly interacting galaxies previously selected from the Sloan Digital Sky Survey (SDSS) as Seyfert-Seyfert pairs based on emission-line ratio diagnostics. Optical slit spectra taken with MODS at the Large Binocular Telescope (LBT) are presented to infer the detailed spatial distribution of optical emission lines, and their line ratios and AGN signatures with respect to the host galaxies, thereby quantifying the impact of beam smearing and large fibre apertures on the spectra captured by the SDSS. We find that at most two of the seven targets actually retain a Seyfert-Seyfert dual AGN, whereas the others may be more likely powered by post-AGB stars in retired galaxies or through shocks in the ISM based on spatially resolved optical line diagnostics. The major cause of this discrepancy is a bias caused by the spillover of flux from the primary source in the secondary SDSS fibre which can be more than an order of magnitude at <3 separations. Previously reported extremely low X-ray-to-[ion{O}{iii}] luminosity ratios may be explained by this misclassification, as can heavily obscured AGN for the primaries. We also find that the nuclei with younger stellar ages host the primary AGN. Studies of close dual AGN selected solely from fibre-based spectroscopy can create severe biases in the sample selection and interpretation of the results. Spatially resolved spectroscopy should ideally be used in the future to characterise such compact systems together with multi-wavelength follow-up observations.
We summarize the optical, UV, and X-ray properties of double-peaked emitters -- AGN with double-peaked Balmer emission lines believed to originate in the AGN accretion disk. We focus on the X-ray spectroscopic results obtained from a new sample of the 16 broadest Balmer line AGN observed with Chandra and Swift.
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