The LIGO-Virgo-KAGRA (LVK) Collaboration has today released its latest catalog of gravitational-wave detections. The data analysed for this update were collected by the twin Laser Interferometer Gravitational-wave Observatory (LIGO) detectors and the Virgo detectors. They are the world's premier observatory of gravitational waves, ripples in the fabric of spacetime.
This catalog aggregates hundreds of cosmic collisions between pairs of black holes, each producing a new, heavier black hole. These distant events provide a rich dataset for scientists to map out how the Universe builds black hole systems.
Using the new data, compiled in the Gravitational-Wave Transient Catalog (GWTC-5.0), scientists from the LVK collaboration and Monash University, have identified clear evidence that black hole binaries are born in distinct sub-populations. Effectively, different cosmic assembly lines that operate in unique environments.
Project lead, Sharan Banagiri, a Research Fellow from Monash University's School of Physics and Astronomy and the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav), used this data to observe the shared characteristics of colliding black holes and neutron stars.
"This set of nearly 400 gravitational-wave detections from LIGO and Virgo provides us with a clear indication that the binary black hole mergers we see are forming in several different ways. Some might form as one giant cloud of gas that collapses to give two massive stars that then become black holes. Others might be black holes that wander into each other in dense environments called clusters that are packed with stars. While others are the product of a previous generation of mergers between two black holes," Dr Banagiri said.
The paper , released as a preprint, found that there is a presence of multiple sub-populations of merging black holes that can potentially arise from different formation pathways.
Assistant Professor of physics at Princeton University, Sylvia Biscoveanu, co-author of the study and previously a Fulbright postgraduate scholar at Monash University, commented on the unprecedented scale of the catalog update.
"GWTC-5 represents the largest single increase in the size of the gravitational-wave catalog, including events with remarkable properties such as GW241127, which contains BHs of very different masses with clearly wobbling orbits due to tilted spins. The new catalog also contains the event with the best localisation on the sky to date, GW240615."
The researchers also found that some of these black holes are spinning very rapidly. These fast spinning black holes have two different sets of masses; the first set are between 10-20 times the sun's mass and the second set have masses greater than 45 times the sun's mass.
"One of the most fascinating things we've discovered about these new black holes is that they are spinning very fast. The sun rotates once every 25 days. If it became a black hole and started spinning as quickly as the ones we discovered, it would be rotating several thousand times every second. So where do these rapidly-spinning black holes come from? One leading explanation is that they are 'hierarchical' products of a previous generation of merger between two black holes," Dr Banagiri said.
The paper identified that black holes which are hierarchical in origin, are more massive than other black holes nearby. By analysing the new data set, the researchers found that the black holes more massive than 45 times the sun, are more likely to merge with lower mass black holes.
The new dataset will provide rich new information about black holes for astronomers and scientists to research.
Chief Investigator at OzGrav and Professor of Physics and Astronomy at Monash University, Eric Thrane, said this is a milestone as gravitational-wave astronomy transitions from the discovery of individual events to the statistical profiling of cosmic population
"We are no longer just looking at individual anomalies, instead, we are seeing a true kaleidoscope of cosmic collisions. We are pushing the edges of what we know, seeing things that are more massive, spinning faster, and more unusual than ever before," Professor Thrane said.
Read the research paper: https://dcc.ligo.org/LIGO-P2600045/public
