The Era of Binary Supermassive Black Holes

Join us for in-depth discussions on planning for the identification of hosts of binary supermassive black holes (MBHs) through coordination between pulsar timing arrays (PTAs) and electromagnetic instruments!

PTAs are expected to begin resolving individual binary MBHs from the gravitational-wave background in the next few years. The first few detections from PTAs will represent the first conclusive identifications of binary supermassive black holes, however will be poorly localized on the sky, potentially spanning regions of up to several thousand square degrees (containing 100’s to 1000’s of candidate galaxies). Therefore, extensive follow-up observations with a broad range of upcoming astrophysical instruments, coupled with historical archives to track long-term signal evolution, will be required to conclusively identify the host galaxies of these systems.

Building toward the first CW detection, significant questions remain that can only be brought through a timely discussion between PTA scientists, electromagnetic observers, and theorists. These critical questions include:

• How can upcoming electromagnetic surveys optimize the balance of sensitivity/field of view for the MMA identification of PTA detections?
• How can PTA and electromagnetic observing communities leverage the large ecosystem of multimessenger coordination infrastructure that have been developed for high-frequency gravitational-wave observations?
• What theorized electromagnetic signatures of binary MBHs require further inspection, and do current/future facilities enable observations of them?
• Are there critical observing capabilities for this science case that are not going to be realized by planned facilities?

As we enter this significant era of first discovery, coordination is crucial: rich science will come from the identification of host galaxies of continuous-wave detections. This pursuit will necessarily involve a broad-strokes multi-wavelength effort, coordinated between PTAs, astronomical archives, new wide-field surveys, and new targeted observations. In this era of imminent continuous-wave detections by PTAs, it will be important to provide a roadmap towards observational coordination between these efforts. This workshop will draw a broad range of electromagnetic and gravitational-wave observers, large-survey scientists, and astronomy cyber-infrastructure scientists, to plan and coordinate such follow-up. We anticipate that this Aspen meeting will facilitate new collaborations and lead to significantly accelerated progress in this field. This conference will include workshop-style elements, bringing together critical players in PTA continuous-wave searches, MBH binary evolution theory, MBH binary observation, multi-messenger cyberinfrastructure, and astronomical observing and archiving facilities to address the above questions and build new collaborative links across the multi-messenger spectrum.

Scientific Organizing Committee:

• Sarah Burke-Spolaor (Chair, sarah.spolaor@mail.wvu.edu)
• Tamara Bogdanovic
• Mike Eracleous
• Matthew Graham
• Kayhan Gultekin (kayhan+aspenw24@umich.edu)
• Jeffrey Hazboun (jeffrey.hazboun@oregonstate.edu)
• Chiara Mingarelli (chiara.mingarelli@yale.edu)
• Gautham Narayan

Event and Participant financial support:

We also gratefully acknowledge support from NANOGrav NSF Physics Frontier Center.

The Gordon and Betty Moore Foundation has generously supported this meeting.

We gratefully acknowledge support from the Research Corporation for Science Advancement: nurturing teacher-scholars and innovative basic research in the physical sciences at American and Canadian colleges and universities since 1912.