English

Clustering effects on the Dark Siren determination of $H_0$: A simulation study

Cosmology and Nongalactic Astrophysics 2025-11-18 v1 Astrophysics of Galaxies General Relativity and Quantum Cosmology

Abstract

Gravitational waves (GWs) offer an alternative way to measure the Hubble parameter. The optimal technique, the ``bright siren'' approach, requires the identification of an electromagnetic counterpart. However, a significant fraction of gravitational waves signals will not have counterparts. Such events can still constrain the Hubble parameter H0H_0 via statistical methods, exploiting galaxy information from the GWs sky localisation volume. In this work, we investigate the power of this method using high-resolution, cosmological simulations that include realistic clustering. We find that clustering leads to increased convergence of the H0H_0 posteriors, with clear recovery of the input value as early as Ngw=40N_{\rm gw}=40 events, compared to uniform catalogues, where the posterior remains largely unconstrained, even with Ngw=100N_{\rm gw}=100 events. In addition, we quantify the role of catalogue incompleteness. We show that catalogues with completeness levels as low as f=25%f=25\% can be competitive with fully complete catalogues, confirming the impact of clustering. Completeness levels of f=50%f=50\% perform statistically similar to complete catalogues with as few as Ngw=40N_{\rm gw}=40 events. This indicates the need to focus on improving gravitational waves detection capabilities, rather than obtaining more complete galaxy catalogues. Finally, we investigate additional properties of the method by taking into consideration physical weights, different observational errors, potential biases from the H0H_0 priors, a variety of detectors' horizon distances, and different methods of catalogue completion and statistical analysis.

Keywords

Cite

@article{arxiv.2511.12334,
  title  = {Clustering effects on the Dark Siren determination of $H_0$: A simulation study},
  author = {Marios Kalomenopoulos and Riccardo Barbieri and Sadegh Khochfar and Jonathan Gair and Robert J. McGibbon},
  journal= {arXiv preprint arXiv:2511.12334},
  year   = {2025}
}

Comments

Submitted in MNRAS, comments welcome!