Nanohertz Gravitational-Wave Constraints on Supermassive Binary Black Holes at Cosmic Dawn

@misc{chen2026nanohertz,
  title = {{Nanohertz Gravitational-Wave Constraints on Supermassive Binary Black Holes at Cosmic Dawn}},
  author = {Yiqin Chen and Shi-Yi Zhao and Xingjiang Zhu and N. D. Ramesh Bhat and Jacob Cardinal Tremblay and Małgorzata Curyło and Valentina Di Marco and George Hobbs and Wenhua Ling and Rami F. Mandow and Richard N. Manchester and Saurav Mishra and Daniel J. Reardon and Sparrow Roch and Christopher J. Russell and Ryan M. Shannon and Jingbo Wang and Shuangqiang Wang and Andrew Zic},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.00613},
  eprint = {2609.00613},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.00613},
}

TY  - UNPB
TI  - Nanohertz Gravitational-Wave Constraints on Supermassive Binary Black Holes at Cosmic Dawn
AU  - Yiqin Chen
AU  - Shi-Yi Zhao
AU  - Xingjiang Zhu
AU  - N. D. Ramesh Bhat
AU  - Jacob Cardinal Tremblay
AU  - Małgorzata Curyło
AU  - Valentina Di Marco
AU  - George Hobbs
AU  - Wenhua Ling
AU  - Rami F. Mandow
AU  - Richard N. Manchester
AU  - Saurav Mishra
AU  - Daniel J. Reardon
AU  - Sparrow Roch
AU  - Christopher J. Russell
AU  - Ryan M. Shannon
AU  - Jingbo Wang
AU  - Shuangqiang Wang
AU  - Andrew Zic
PY  - 2026
DA  - 2026/09/01
PB  - arXiv
DO  - 10.48550/arxiv.2609.00613
UR  - https://arxiv.org/abs/2609.00613
AB  - Standard continuous gravitational-wave searches with pulsar timing arrays (PTAs) neglect cosmological redshift, restricting their applicability to the local Universe. We introduce a redshift-aware PTA framework and apply it to the Parkes PTA Data Release 3, deriving the first direct constraints on supermassive binary black holes (SMBBHs) at the cosmic dawn. Evaluating our limits across a broad redshift range, we observationally establish the non-monotonic mass-redshift exclusion boundary driven by the theoretical ``redshift bias", demonstrating how PTAs can effectively probe sources at extreme distances. Redshift-aware targeted searches toward high-redshift systems, including the ultraluminous quasar J0100+2802 (z=6.327) and the JWST-discovered galaxy JADES-GS-z14-0 (z=14.32), rigorously exclude SMBBHs with chirp masses ℳ_c ≳ 10^10 M_⊙ across the nanohertz frequency band. Finally, we demonstrate that high-redshift binaries can be robustly detected and localized, allowing for the accurate measurement of their intrinsic properties. Our results provide the tightest constraints to date on SMBBHs at z > 6 and establish a practical framework for probing early-Universe black hole assembly.
ER  -