Abstract

Last year, several collaborations reported evidence for a background of low-frequency gravitational waves pervading the universe. The most credible source of this gravitational wave background is a cosmological population of merging supermassive black holes, offering insights into the growth history of the largest black holes in the universe. Additionally, the signal may also contain contributions from other processes in the early universe, potentially revealing new physics. The gravitational wave background was inferred by carefully observing an array of pulsars over many years. In this talk, I’ll explain the discovery, and describe our efforts to test the consistency of the signal seen by the NANO Grav collaboration. By systematically removing pulsars from the pulsar array, we studied how the recovered signal changed, helping us to verify its robustness.