We use the recent statistics of dual active galactic nuclei (AGN) in the
$James Webb Space Telescope$ (JWST) data at $z sim 3.4$ to address two
aspects of the feedback and evolution scenarios of supermassive black hole
binaries (SMBHB). We find that the JWST data provide evidence for the members
of a binary black hole being ‘lit’ at the same time, rather than independently
— a scenario which is consistent with gas-rich mergers being responsible for
concurrent AGN activity. This conclusion is supported by the recent NANOGrav
Pulsar Timing Array (PTA) measurements, whose upper limits on the stochastic
gravitational wave strain amplitude lie below those expected from extrapolating
the dual AGN fraction. The results indicate either a ‘stalling’ of the binaries
at the separations probed by NANOGrav, or rapid gas-driven inspirals.


The recent statistics from the James Webb Space Telescope (JWST) data at z ~ 3.4 have provided evidence for the members of a binary black hole being active at the same time, rather than independently. This suggests that gas-rich mergers may be responsible for concurrent activity in supermassive black hole binaries (SMBHB). These findings are consistent with the recent measurements by the NANOGrav Pulsar Timing Array (PTA), which indicate upper limits on the gravitational wave strain amplitude below what would be expected from extrapolating the dual AGN fraction. This suggests that the binaries may either be stalling at the separations probed by NANOGrav or undergoing rapid gas-driven inspirals.

Future Roadmap:

Looking ahead, further research and observation in the field of dual active galactic nuclei (AGN) and supermassive black hole binaries (SMBHB) are essential to gain a deeper understanding of their feedback mechanisms and evolution scenarios. Here is a potential roadmap for readers interested in this topic:

1. Investigate Gas-rich Mergers:

One avenue for future research is to explore the role of gas-rich mergers in triggering concurrent AGN activity in SMBHB. Researchers can analyze more data from JWST and other observatories to gather additional evidence supporting this scenario. This would help validate the conclusion drawn from the current JWST data.

2. Study Binary Black Hole Stalling:

Another important area of research is to investigate the possibility of binaries stalling at specific separations. To address this, scientists could conduct simulations and modeling studies to understand the physical processes that might cause this stalling effect. By comparing theoretical predictions with observational data, insights into this phenomenon can be gained.

3. Explore Rapid Gas-driven Inspirals:

The idea of rapid inspirals driven by gas is also worth further investigation. Researchers can study the dynamics of gas accretion onto SMBHB and explore how it affects their inspiral rates. This could involve numerical simulations and theoretical modeling to understand the conditions under which rapid inspirals can occur. Observational data from a variety of telescopes, including JWST, can be used to test these theoretical predictions.

4. Validate NANOGrav PTA Measurements:

The upper limits on gravitational wave strain amplitude provided by the NANOGrav Pulsar Timing Array (PTA) measurements may indicate important insights into the behavior of SMBHB. Future studies could focus on validating these measurements and determining whether the observed gaps between the expected and measured values are indicative of a stalling scenario or rapid inspirals. This could involve refining the measurements or exploring alternative explanations for the discrepancies.

Challenges and Opportunities:

While conducting research in the field of dual AGN and SMBHB, there are several challenges and opportunities on the horizon:

  • Data Limitations: The availability and quality of observational data might pose limitations to further research. Efforts should be made to collect more high-resolution data from observatories like JWST and future space missions.
  • Complexity of Simulations: Simulating the dynamics of gas-rich mergers and binary black hole inspirals can be computationally intensive and require advanced modeling techniques. Researchers should focus on developing more efficient and accurate simulation methods to address these challenges.
  • Collaboration and Interdisciplinary Approach: Addressing the open questions in this field may require collaboration between astronomers, astrophysicists, and experts in numerical simulations and data analysis. Interdisciplinary approaches can provide different perspectives and advance our understanding of the subject.
  • New Observational Techniques: The development of novel observational techniques and instruments will be crucial in observing and studying dual AGN and SMBHB with higher precision. Researchers should explore opportunities to propose and develop new observational facilities or modifications to existing ones.
  • Human-made Gravitational Wave Detectors: The current limitations of gravitational wave observations from sources like NANOGrav PTA could be overcome by the development of more sensitive, human-made gravitational wave detectors. Advancements in this technology would greatly contribute to studying the behavior and properties of SMBHB.

By addressing these challenges and embracing the opportunities, researchers can make significant progress in unraveling the feedback and evolution scenarios of supermassive black hole binaries and improving our understanding of the processes that shape the universe.

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