Two in one? A possible dual radio-emitting nucleus in the quasar SDSS J1425+3231

Abstract

The radio‐emitting quasar SDSS J1425+3231 (z = 0.478) was recently found to have double‐peaked narrow [O iii] optical emission lines. Based on the analysis of the optical spectrum, Peng et al. suggested that this object harbours a dual active galactic nucleus (AGN) system, with two supermassive black holes (SMBHs) separated on a kpc scale. SMBH pairs should be ubiquitous according to hierarchical galaxy formation scenarios in which the host galaxies and their central black holes grow together via interactions and eventual mergers. Yet the number of presently confirmed dual SMBHs on kpc or smaller scales remains small. A possible way to obtain direct observational evidence for duality is to conduct high‐resolution radio interferometric measurements, provided that both AGN are in an evolutionary phase when some activity is going on in the radio. We used the technique of very long baseline interferometry (VLBI) to image SDSS J1425+3231. Observations made with the European VLBI Network at 1.7‐ and 5‐GHz frequencies in 2011 revealed compact radio emission at sub‐mJy flux density levels from two components with a projected linear separation of ∼2.6 kpc. These two components support the possibility of a dual AGN system. The weaker component remained undetected at 5 GHz due to its steep radio spectrum. Further study will be necessary to securely rule out a jet–shock interpretation of the less dominant compact radio source. Assuming the dual AGN interpretation, we discuss black hole masses, luminosities and accretion rates of the two components using available X‐ray, optical and radio data. While high‐resolution radio interferometric imaging is not an efficient technique to search blindly for dual AGN, it is an invaluable tool to confirm the existence of selected candidates.

Prompt electromagnetic transients from binary black hole mergers

“…Their peak efficiency is reached at a similar time after merger as in our simulations, but remains smaller than our peak value [Eq. (20)] by a factor of a few.…”

“…A number of mechanisms may provide signals associated with these sources across a broad range of time scales from ∼10 9 years before merger to ∼10 9 years after merger [13]. Considerable evidence for binary SMBH systems has already been observed, but is restricted to those either well before merger [14][15][16][17][18][19][20][21], or well after merger [22][23][24][25][26][27][28].…”

Four Dual Agn Candidates Observed With the Vlba

“…However, further observations of these candidate sources with high resolution found that only 1% of them could be genuine dual AGNs (Fu et al 2011a); in most of the sources this spectral behavior can be be explained by other effects not requiring dual AGNs (Heckman et al 1981(Heckman et al , 1984Xu & Komossa 2009;Crenshaw et al 2010). As shown by several works (e.g., Fischer et al 2011;Fu et al 2011a;Shen et al 2011;Tingay & Wayth 2011;Frey et al 2012;An et al 2013;Comerford et al 2013;Gabányi et al 2014;Kharb et al 2015;McGurk et al 2015), doublepeaked narrow lines alone are not good indicators to select compelling dual AGN candidates, other diagnostic methods have to be used. Comerford et al (2012) used high-resolution long-slit spectroscopy to select the most compelling dual AGN candidates from the double-peaked narrow emission line active galaxies.…”

Wise J233237.05–505643.5: A Double-Peaked, Broad-Lined Active Galactic Nucleus With a Spiral-Shaped Radio Morphology

“…The radio galaxy 4C37.11 contains a SMBH binary system with a 7.3 pc separation and ∼1.5 × 10 8 M in mass (Rodriguez et al 2006). In addition, there are several radio-bright DPEs in which double nuclei with separations of a few kpc are seen in high-resolution radio mapping, such as SDSS J1536+0441 (Wrobel & Laor 2009;Bondi & Pérez-Torres 2010), SDSS J1502+1115 (Fu et al 2011b), and SDSS J1425+3231 (Frey et al 2012). These results indicate that some DPE systems indeed host dual AGNs.…”