Uncovering the Origin of Black Hole Mergers using Orbital Eccentricity

The award supports research on the origin of black hole mergers discovered by NSF's LIGO gravitational-wave observatory, in collaboration with the Virgo and KAGRA gravitational wave detectors. The discovery of gravitational waves opened a new window on the Universe, providing information on cosmic events that previously proved inaccessible. Black hole mergers can elucidate where Einstein's general theory of relativity might break down, how stars and other astrophysical objects evolve, and how the Universe is expanding. During the award period, LIGO, Virgo and KAGRA are expected to observe an unprecedented number of black hole mergers, far exceeding all previous detections combined, enabling new probes of the underlying processes. It will also provide opportunity for the detection of special events that make up a small fraction of mergers but carry unique information about parts of the Universe. The research will probe the origin of black hole mergers utilizing an observational fingerprint that can help distinguish between different astrophysical formation scenarios: orbital eccentricity. The project will carry out the full range of tasks needed to gain astrophysical insight from recorded gravitational wave data: it will search for eccentric mergers during LIGO-Virgo-KAGRA observing runs throughout the award period; it will examine the recoverable properties of the discovered events to establish their possible eccentricity; and it will compare observed events with expectations from multiple formation scenarios to uncover the astrophysical origin of the detected black hole mergers. A significant part of the work will be carried out by students, helping advance the education of a globally competitive STEM workforce. Students will acquire strong computational and data science skills and will contribute to the national cyberinfrastructure required for multi-messenger observation campaigns. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.