Simons Center for Computational Astrophysics
"Insights into Supermassive Black Hole Mergers, Stalling and Demographics with Pulsar Timing Arrays"
Galaxy mergers are a standard aspect of galaxy formation and evolution, and likely all large galaxies contain central supermassive black holes (SMBH). Here I discuss a new bottom-up approach to identifying continuous nanohertz gravitational wave (GW) host galaxies by using massive elliptical galaxies in the 2 Micron All Sky Survey, assessing the likelihood of detecting one of these sources with Pulsar Timing Arrays (PTAs), their contribution to the GW background and its anisotropy, and report on the characteristics of the most detected SMBH binaries and host galaxies. We find that out to 225 Mpc there are on average 91 sources emitting GWs in the PTA band and 7 stalled binaries. The chance of detecting these GW sources with current PTA data is <1%, however in the next 10 years PTAs probe a region of the parameter space rich in sources, making a 3-sigma (or better) detection likely, depending on the source position of the sky and the ability to subtract the GW background.