The Emerging Population of Gravitational Wave Sources

  • July 29, 2019, 2:00 pm US/Central
  • Curia II
  • Will Farr, Stony Brook University / Center for Computational Astrophysics, Flatiron Institute
  • Gordan Krnjaic

Abstract:  The last four years have been a bonanza for gravitational wave astronomy.  The first gravitational wave signal ever detected—GW150914, the merger of a 30- and a 40-solar mass black hole—was followed by nine more announced black hole mergers in Advanced LIGO’s first and second observing runs (several were also observed in the Virgo detector).  The third observing run, currently ongoing, has produced about 15 more public alerts of likely black hole mergers.  Two years ago, the first observed merger of two neutron stars (GW170817) was also detected in the electromagnetic spectrum, in a collective effort involving almost 4000 astronomers around the world.  Each of these events carries a wealth of information about the merging objects, their progenitors, their environment, and the universe; however, to extract this information we must often resort to statistical methods that extract features collectively from the entire population of events.  I will run through a few highlights from individual detections (including the measurement of the Hubble constant from GW170817), and then discuss recent results in modeling the population of merging compact objects including: using the distribution of spins in the population to distinguish among competing formation mechanisms; measuring the distribution of merger events in redshift to determine that we live—and gravity propagates—in three spatial dimensions (who knew?) and (eventually) measure the star formation rate to sub-percent precision; and measuring the maximum mass of stellar-mass black holes and using this feature in the mass spectrum for cosmography.