Gravity seminar: Inference of H0 using the clustering information of the large scale structure, Sayantani Bera (IUCAA Pune)

The standard sirens in the GW astronomy provide us with a direct measure of the cosmological distances independent of the cosmic distance ladder. When accompanied by an optical counterpart, it can also provide a redshift measurement, thus constraining the Hubble parameter H₀, like in the case of the event GW170817. But, for the majority of the detected GW events, it is not possible to obtain an EM counterpart. Such sources with unknown redshifts can also be used to infer H₀, by making use of the clustering of the galaxies. In this talk, I will show how the angular clustering between gravitational-wave standard sirens and galaxies with known redshifts allows an inference of H₀, regardless of whether the host galaxies of any of these sirens are present in the galaxy catalog. With a realistic simulation of the GW events detected with a three-detector network, it is shown that the cross-correlation technique infers the Hubble parameter with a precision of less than 10% (2%) at 90% confidence with 50 (500) sources, even with a 100% incomplete catalog. I will point out the important difference between our method and the current state-of-the-art technique adopted in the LVK work.