Limits on first structure formation from pulsar timing

Abstract

© International Astronomical Union 2016.By monitoring the arrival times from millisecond pulsars for years to decades, it is possible to search for, or place limits on, nanohertz frequency gravitational radiation. The most promising source of gravitational waves in this band is a stochastic background emitted from a population of supermassive black hole binaries. As these binaries are the direct product of of galaxy mergers and the properties of the SMBHs correlated strongly with their host galaxies, the gravitational wave emission of the binaries can be used to study how galaxies evolve. Here I discuss how pulsar timing can be used to search for gravitational waves, and how limits on the strength of the background are being used to challenge models of supermassive black hole formation and evolution.