Dark siren cosmology with binary black holes in the era of third-generation gravitational wave detectors

Third-generation (3G) gravitational wave detectors, in particular Einstein Telescope (ET) and Cosmic Explorer (CE), will explore unprecedented cosmic volumes in search for compact binary mergers, providing us with tens of thousands of detections per year. In this study, we simulate and employ binary black holes detected by 3G interferometers as dark sirens, to extract and infer cosmological parameters by cross-matching gravitational wave data with electromagnetic information retrieved from a simulated galaxy catalog. Considering a standard $\Lambda$CDM model, we apply a suitable Bayesian framework to obtain joint posterior distributions for the Hubble constant $H_0$ and the matter energy density parameter $\Omega_m$ in different scenarios. Assuming a galaxy catalog complete up to $z=1$ and dark sirens detected with a network signal-to-noise ratio greater than 300, we show that a network made of ET and two CEs can constrain $H_0$ ($\Omega_m$) to a promising $0.8\%$ ($10.0\%$) at $90\%$ confidence interval within one year of continuous observations. Additionally, we find that most of the information on $H_0$ is contained in local, single-host dark sirens, and that dark sirens at $z>1$ do not substantially improve these estimates. Our results imply that a sub-percent measure of $H_0$ can confidently be attained by a network of 3G detectors, highlighting the need for characterising all systematic effects to a higher accuracy.Comment: 23 pages, 8 figures. Major update on results, updated figures, v2 accepted for publication in PR

Science with the Einstein Telescope: a comparison of different designs

The Einstein Telescope (ET), the European project for a third-generation gravitational-wave detector, has a reference configuration based on a triangular shape consisting of three nested detectors with 10 km arms, where in each arm there is a `xylophone' configuration made of an interferometer tuned toward high frequencies, and an interferometer tuned toward low frequencies and working at cryogenic temperature. Here, we examine the scientific perspectives under possible variations of this reference design. We perform a detailed evaluation of the science case for a single triangular geometry observatory, and we compare it with the results obtained for a network of two L-shaped detectors (either parallel or misaligned) located in Europe, considering different choices of arm-length for both the triangle and the 2L geometries. We also study how the science output changes in the absence of the low-frequency instrument, both for the triangle and the 2L configurations. We examine a broad class of simple `metrics' that quantify the science output, related to compact binary coalescences, multi-messenger astronomy and stochastic backgrounds, and we then examine the impact of different detector designs on a more specific set of scientific objectives.Comment: 197 pages, 72 figure

Dark siren cosmology with binary black holes in the era of third-generation gravitational wave detectors

International audienceThird-generation (3G) gravitational wave detectors, in particular Einstein Telescope (ET) and Cosmic Explorer (CE), will explore unprecedented cosmic volumes in search for compact binary mergers, providing us with tens of thousands of detections per year. In this study, we simulate and employ binary black holes detected by 3G interferometers as dark sirens, to extract and infer cosmological parameters by cross-matching gravitational wave data with electromagnetic information retrieved from a simulated galaxy catalog. Considering a standard $\Lambda$CDM model, we apply a suitable Bayesian framework to obtain joint posterior distributions for the Hubble constant $H_0$ and the matter energy density parameter $\Omega_m$ in different scenarios. Assuming a galaxy catalog complete up to $z=1$ and dark sirens detected with a network signal-to-noise ratio greater than 300, we show that a network made of ET and two CEs can constrain $H_0$ ($\Omega_m$) to a promising $0.7\%$ ($9.0\%$) at $90\%$ confidence interval within one year of continuous observations. Additionally, we find that most of the information on $H_0$ is contained in local, single-host dark sirens, and that dark sirens at $z>1$ do not substantially improve these estimates. Our results imply that a sub-percent measure of $H_0$ can confidently be attained by a network of 3G detectors, highlighting the need for characterising all systematic effects to a higher accuracy

Multiband gravitational wave cosmology with stellar origin black hole binaries

International audienceMassive stellar origin black hole binaries (SBHBs), originating from stars above the pair-instability mass gap, are primary candidates for multiband gravitational wave (GW) observations. Here we study the possibility to use them as effective dark standard sirens to constrain cosmological parameters. The long lasting inspiral signal emitted by these systems is accessible by the future Laser Interferometer Space Antenna (LISA), while the late inspiral and merger are eventually detected by third generation ground-based telescopes such as the Einstein Telescope (ET). The direct measurement of the luminosity distance and the sky position to the source, together with the inhomogeneous redshift distribution of possible host galaxies, allow us to infer cosmological parameters by probabilistic means. The efficiency of this statistical method relies in high parameter estimation performances. We show that this multiband approach allows a precise determination of the Hubble constant H0 with just O(10) detected sources. For selected SBHB population models, assuming 4 (10) years of LISA observations, we find that H0 is typically determined at ∼2% (∼1.5%), whereas Ωm is only mildly constrained with a typical precision of 30% (20%). We discuss the origin of some outliers in our final estimates and we comment on ways to reduce their presence