Probing cosmology with the Fifth Gravitational-Wave Transient Catalogue and the Euclid Q1 catalogue
Sarah Ferraiuolo (CPPM Marsiglia & Sapienza Università di Roma)
Tuesday 10/11/2026 @ 14:00, Sala Antonio Sollima (IV piano Battiferro)
Galaxy catalogues are a key ingredient of the dark siren method, which allows cosmological parameters to be inferred from gravitational-wave (GW) events without an electromagnetic counterpart. In this talk, I will present the first end-to-end dark siren analysis using Euclid data. I will begin with an overview of the galaxy catalogues already released and planned by the Euclid mission, and of their overlap with the 236 confident events of the Fifth Gravitational-Wave Transient Catalogue (GWTC-5.0). I will then characterise the galaxy luminosity function and the completeness of the Euclid Quick Data Release 1 (Q1) catalogue, using an incompleteness model that also accounts for saturation at the bright end. Because of the limited Q1 footprint (about 65 deg²), only two GWTC-5.0 events have good coverage within the catalogue, and the resulting constraint on H0 is comparable to that obtained from the GW population alone. Nevertheless, this work sets up an analysis pipeline ready for Euclid DR1, whose much larger area will overlap many more GW events, and is a first step toward establishing Euclid as a key resource for dark siren cosmology.