LoTSS of dual AGN: enhanced detectability and prospects for a systematic search
Abstract
Context: Dual active galactic nuclei (DAGN) - systems of two accreting supermassive black holes at kpc-scale separations - trace galaxy mergers and are the progenitors of gravitational-wave sources targeted by pulsar timing arrays and the upcoming Laser Interferometer Space Antenna. However, their radio properties remain poorly constrained, particularly at high redshift. Aims: We demonstrate the detectability of high-redshift DAGN at 144 MHz through sub-arcsec imaging of the LOFAR Two-metre Sky Survey (LoTSS) and characterize their low-frequency radio properties. Methods: We cross-matched 92 spectroscopically confirmed DAGN (z > 0.3, projected separation r_p < 30 kpc) with the LoTSS DR2 catalog and reprocessed international LOFAR telescope (ILT) data for three systems (0.59 < z < 2.39), achieving ~0.3 arcsec resolution at 144 MHz. Multi-frequency analysis and brightness-temperature diagnostics were used to investigate the radio emission. Results: We obtained high-quality ILT images for all three systems. In one source at z = 1.49, both AGN are detected at >5 sigma, making it one of the highest-redshift and faintest radio-detected DAGN. Brightness temperatures confirm AGN-powered emission even in sub-mJy sources. In the other two systems only one AGN is detected; for one, the new data constrain the low-frequency spectrum of a compact steep-spectrum source, indicating that its morphology is driven by jet-ISM interaction rather than the companion galaxy. For the 92 objects sample, the LoTSS detection rate is ~24%, significantly higher than for matched single AGN (~9-10%), suggesting an enhanced detectability of DAGN in the LoTSS. Conclusions: Low-frequency sub-arcsec radio observations provide an efficient, dust-unbiased method to detect and characterize DAGN. This pilot study establishes a benchmark for the forthcoming all-sky ~0.3 arcsec iLoTSS survey and future SKA observations.
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BibTeX
@misc{damato2026lotss,
title = {{LoTSS of dual AGN: enhanced detectability and prospects for a systematic search}},
author = {Q. D'Amato and F. Mannucci and E. De Rubeis and I. Prandoni and A. De Rosa and M. Scialpi and M. Kunert-Bajraszewska and A. Janiuk and A. Krauze and L. Battistini and E. Bertola and C. Bracci and A. Chakraborty and M. Ceci and C. Cicone and G. Cresci and A. Marconi and C. Marconcini and E. Nardini and M. Parvatikar and A. Peca and K. Rubinur and P. Severgnini and C. Spingola and L. Ulivi and G. Venturi and C. Vignali and M. V. Zanchettin},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.22449},
eprint = {2609.22449},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.22449},
note = {CC BY-NC-SA 4.0},
}
RIS
TY - UNPB
TI - LoTSS of dual AGN: enhanced detectability and prospects for a systematic search
AU - Q. D'Amato
AU - F. Mannucci
AU - E. De Rubeis
AU - I. Prandoni
AU - A. De Rosa
AU - M. Scialpi
AU - M. Kunert-Bajraszewska
AU - A. Janiuk
AU - A. Krauze
AU - L. Battistini
AU - E. Bertola
AU - C. Bracci
AU - A. Chakraborty
AU - M. Ceci
AU - C. Cicone
AU - G. Cresci
AU - A. Marconi
AU - C. Marconcini
AU - E. Nardini
AU - M. Parvatikar
AU - A. Peca
AU - K. Rubinur
AU - P. Severgnini
AU - C. Spingola
AU - L. Ulivi
AU - G. Venturi
AU - C. Vignali
AU - M. V. Zanchettin
PY - 2026
DA - 2026/09/18
PB - arXiv
DO - 10.48550/arxiv.2609.22449
UR - https://arxiv.org/abs/2609.22449
AB - Context: Dual active galactic nuclei (DAGN) - systems of two accreting supermassive black holes at kpc-scale separations - trace galaxy mergers and are the progenitors of gravitational-wave sources targeted by pulsar timing arrays and the upcoming Laser Interferometer Space Antenna. However, their radio properties remain poorly constrained, particularly at high redshift. Aims: We demonstrate the detectability of high-redshift DAGN at 144 MHz through sub-arcsec imaging of the LOFAR Two-metre Sky Survey (LoTSS) and characterize their low-frequency radio properties. Methods: We cross-matched 92 spectroscopically confirmed DAGN (z > 0.3, projected separation r_p < 30 kpc) with the LoTSS DR2 catalog and reprocessed international LOFAR telescope (ILT) data for three systems (0.59 < z < 2.39), achieving ~0.3 arcsec resolution at 144 MHz. Multi-frequency analysis and brightness-temperature diagnostics were used to investigate the radio emission. Results: We obtained high-quality ILT images for all three systems. In one source at z = 1.49, both AGN are detected at >5 sigma, making it one of the highest-redshift and faintest radio-detected DAGN. Brightness temperatures confirm AGN-powered emission even in sub-mJy sources. In the other two systems only one AGN is detected; for one, the new data constrain the low-frequency spectrum of a compact steep-spectrum source, indicating that its morphology is driven by jet-ISM interaction rather than the companion galaxy. For the 92 objects sample, the LoTSS detection rate is ~24%, significantly higher than for matched single AGN (~9-10%), suggesting an enhanced detectability of DAGN in the LoTSS. Conclusions: Low-frequency sub-arcsec radio observations provide an efficient, dust-unbiased method to detect and characterize DAGN. This pilot study establishes a benchmark for the forthcoming all-sky ~0.3 arcsec iLoTSS survey and future SKA observations.
ER -