Gravitational-wave and electromagnetic detections in the context of the CosmoDC2 LSST synthetic catalog

TL;DR

This work delivers CosmoDC2_BCO, a self-consistent synthetic catalog of gravitational-wave events and electromagnetic kilonova counterparts anchored to the LSST CosmoDC2 galaxy catalog, enabling realistic multi-messenger forecasts. It advances a framework that couples astrophysical merger-rate templates with host-galaxy properties, simulates detector networks from LVK to CE and ET, and produces both GW parameter covariances via Fisher inference and EM kilonova photometry. The major contributions include quantified gains in detections and parameter precision from 3G networks, a demonstrated ongoing value of 2G detectors for localization and distance inference, and a realistic assessment of kilonova yields under LSST-like follow-up with duty-cycle impacts. The work provides a public, three-catalog data release (Input, Output, Kilonova VAC) and highlights the practical implications for dark and bright siren cosmology, while noting substantial uncertainties tied to merger rates, kilonova luminosities, and survey scheduling that warrant cautious interpretation and future refinement.

Abstract

We release CosmoDC2_BCO, a synthetic catalog of gravitational-wave events and electromagnetic counterparts associated with galaxies from CosmoDC2. The catalog provides intrinsic and extrinsic source parameters, signal-to-noise ratios, parameter uncertainties, sky localization areas, and kilonova apparent magnitudes in LSST filters. Our results show that third-generation detector networks substantially increase detection rates and improve parameter estimation. Second-generation detectors, when combined with third-generation ones, significantly enhance sky localization and distance precision, particularly for BNS mergers. Assuming a simplified Target of Opportunity strategy, we estimate that an LSST-like survey, partnered with the CE+ET+LVK network at 70% duty cycle, could detect about 5000 kilonovae with GW counterparts over a 10-year period on a 16000 deg^2 footprint, predominantly from low-mass BNS mergers that produce long-lived supermassive neutron star remnants. While this is a substantial number, it represents only a small fraction of the total neutron star mergers expected to be observed by third-generation networks. These projections rely on several simplifying assumptions-including the adopted merger rate, the kilonova luminosity distribution, and the configuration and scheduling of future surveys-which introduce notable uncertainties. Therefore, the estimated detection numbers should be interpreted with appropriate caution.

Figures (18)

• Figure 1: Workflow for generating gravitational-wave catalogs.
• Figure 2: Merger rate density as a function of mass at fixed redshifts (left) and as a function of redshift at fixed masses (right) for BBH (top), BHNS (middle), and BNS (bottom). See Section \ref{['HG_models_sec']} for details.
• Figure 3: Total source-frame merger rate as a function of redshift, obtained by integrating over the full mass range. The legend indicates the expected number of merger events within a sky area of 440 square degrees over a period of 10 years.
• Figure 4: Tiling scheme used to extend the CosmoDC2 sky coverage to match the LSST survey area. The replicated tiles do not strictly follow the LSST footprint but are arranged to account for variations in the network pattern function across the sky while preserving a realistic sky distribution for dark siren cosmology studies.
• Figure 5: Density distribution of primary mass $m_1$ and mass ratio $q$ for the simulated events. See Section \ref{['sec:mass-dist']} for details.