Varstrometry selected radio-loud candidates of dual and off-nucleus quasars at sub-kpc scales

Wang, Hao-Chen; Wang, Junxian; Gu, Minfeng; Liao, Mai

doi:10.1093/mnrasl/slad069

Cited by 3 publications

(4 citation statements)

References 36 publications

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“…The above two VLBA-detected sources have large astrometric − excess − noise (AEN) in the Gaia DR3 catalog, which indicates their significant disagreements between Gaia observations and the best-fitting standard astrometric models (Lindegren et al 2021). The AEN has a significant dependence on Gaia magnitude (e.g., Wang et al 2023c). Therefore, the large AENs in our target sources could be caused by their dark Gaia g-band magnitudes (>20).…”

Section: Astrometric Analysismentioning

confidence: 85%

Very Long Baseline Array Observations of Parsec-scale Radio Emission in Dual Active Galactic Nuclei

Xu,

Cui,

Liu

et al. 2024

ApJ

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It is believed that dual active galactic nuclei (AGN) form during galaxy mergers. Studying dual-AGN emission can provide valuable insights into galaxy merging and evolution. To investigate parsec-scale radio emission properties, we observed eight radio components of four selected dual-AGN systems using the Very Long Baseline Array (VLBA) at 5 GHz in multiple-phase-center mode. Among them, two compact radio components, labeled J0051+0020B and J2300-0005A, were detected clearly on parsec scales for the first time. However, the radio emission of the other six components was resolved out in the high-resolution images. We provide the values or upper limits of the brightness temperature and radio emission power, and analyze the emission origins in detail for each target. Based on their physical properties reported in this work and in the literature, we suggest that the radio emission in J0051+0020B and J2300-0005A originates primarily from compact jets, while the other six sources show more complex emission mechanisms. In addition, our VLBA observations suggest that the systematic X-ray deficit in our dual-AGN sample is likely attributed to the tidally induced effect and possibly a viewing angle effect.

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Section: Astrometric Analysismentioning

confidence: 85%

Very Long Baseline Array Observations of Parsec-scale Radio Emission in Dual Active Galactic Nuclei

Xu,

Cui,

Liu

et al. 2024

ApJ

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“…The radio spectrum for this target is likely curved, though there are archival flux densities significantly offset from the model that might indicate flux density variability over years-long timescales. Recently, Wang et al (2023) found, from new e-MERLIN observations of this target, a significant and large Gaia-radio offset.…”

Section: Individual Targetsmentioning

confidence: 89%

“…The radio spectrum for this target is curved, with a peak frequency of 1.67 GHz and a curved spectral index of 0.46. Recently, Wang et al (2023) found, from new e-MERLIN observations of this target, a significant and large Gaia-radio offset.…”

Section: Individual Targetsmentioning

confidence: 89%

VaDAR: Varstrometry for Dual AGN Using Radio Interferometry

Schwartzman,

Clarke,

Nyland

et al. 2024

ApJ

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Binary and dual active galactic nuclei (AGNs) are an important observational tool for studying the formation and dynamical evolution of galaxies and supermassive black holes. An entirely new method for identifying possible AGN pairs makes use of the exquisite positional accuracy of Gaia to detect astrometrically variable quasars, in tandem with the high spatial resolution of the Karl G. Jansky Very Large Array (VLA). We present a new pilot study of radio observations of 18 quasars (0.8 ≤ z ≤ 2.9), selected from the Sloan Digital Sky Survey DR16Q and matched with the Gaia DR3. All 18 targets are identified by their excess astrometric noise in Gaia. We targeted these 18 quasars with the VLA at 2–4 GHz (S band) and 8–12 GHz (X band), providing resolutions of 0.″65 and 0.″2, respectively, in order to constrain the origin of this variability. We combine these data with ancillary radio survey data and perform radio spectral modeling. The new observations are used to constrain the driver of the excess astrometric noise. We find that ∼44% of the target sample is likely to be either candidate dual AGN or gravitationally lensed quasars. Ultimately, we use this new strategy to help identify and understand this sample of astrometrically variable quasars, demonstrating the potential of this method for systematically identifying kiloparsec-scale dual quasars.

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“…Gaia astrometry in comparison with VLBI astrometry is useful for studying jet systems of quasars (Kovalev et al 2017;Makarov et al 2017;Petrov et al 2019;Plavin et al 2019) or discovering binary/off-nucleus quasars (Skipper & Browne 2018;Breiding et al 2021). A recent study using varstrometry with e-MERLIN revealed four targets with Gaiaradio offsets of ∼960 mas (Wang et al 2023), highlighting the potential of varstrometry to uncover candidate dual/off-nucleus quasars. In addition to binary SMBHs, VLBI was also used to search for strong gravitational lenses on milliarcsecond scales (Casadio et al 2021), which might be detected by varstrometry.…”

Section: Introductionmentioning

confidence: 99%

Varstrometry for Off-nucleus and Dual Sub-kiloparsec Active Galactic Nuclei (VODKA): Very Long Baseline Array Searches for Dual or Off-nucleus Quasars and Small-scale Jets

Chen,

Liu,

Lazio

et al. 2023

ApJ

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Dual and off-nucleus active supermassive black holes are expected to be common in the hierarchical structure formation paradigm, but their identification at parsec scales remains a challenge due to strict angular resolution requirements. We conducted a systematic study using the Very Long Baseline Array (VLBA) to examine 23 radio-bright candidate dual and off-nucleus quasars. The targets are selected by a novel astrometric technique (varstrometry) from Gaia, aiming to identify dual or off-nucleus quasars at (sub)kiloparsec scales. Among these quasars, eight exhibit either multiple radio components or significant (>3σ) positional offsets between the VLBA and Gaia positions. The radio emission from the three candidates, which exhibit multiple radio components, is likely to originate from small-scale jets based on their morphology. Among the remaining five candidates with significant VLBA-Gaia offsets, three are identified as potential dual quasars at parsec scales, one is likely attributed to small-scale jets, and the origin of the last candidate remains unclear. We explore alternative explanations for the observed VLBA-Gaia offsets. We find no evidence for optical jets at kiloparsec scales, nor any contamination to Gaia astrometric noise from the host galaxy; misaligned coordinate systems are unlikely to account for our offsets. Our study highlights the promise of the varstrometry technique in discovering candidate dual or off-nucleus quasars and emphasizes the need for further confirmation and investigation to validate and understand these intriguing candidates.

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Varstrometry selected radio-loud candidates of dual and off-nucleus quasars at sub-kpc scales

Cited by 3 publications

References 36 publications

Very Long Baseline Array Observations of Parsec-scale Radio Emission in Dual Active Galactic Nuclei

Very Long Baseline Array Observations of Parsec-scale Radio Emission in Dual Active Galactic Nuclei

VaDAR: Varstrometry for Dual AGN Using Radio Interferometry

Varstrometry for Off-nucleus and Dual Sub-kiloparsec Active Galactic Nuclei (VODKA): Very Long Baseline Array Searches for Dual or Off-nucleus Quasars and Small-scale Jets

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