arXiv subjects

Matteo Tagliazucchi

Publications and source records attributed to Matteo Tagliazucchi.

9 recordsLinked to original sources

arXiv2026

Not all those missing are lost: leveraging galaxy clustering in incomplete catalogs to unleash dark sirens cosmology

Gravitational waves offer a unique opportunity to solve the Hubble tension. In order to do so, we have to extract as much information as possible from cross correlating gravitational wave events (used as "dark sirens") with incomplete galaxy catalogs. Traditional methods assume a uniform in comoving volume distribution for galaxies missing from the catalogs, which neglects the fact that galaxies tend to cluster, leading to less precise and possibly biased posteriors. In this paper, we introduce a new method for accounting for galaxy clustering when dealing with an incomplete galaxy catalog, by adding back galaxies to the incomplete catalog and distributing them in pixels according to the correlation function $\xi(r)$. We find that our method drastically improves on traditional ones when the galaxy catalog is only $1\%-10\%$ complete, leading to posteriors that are between 2 and 4 times as precise, depending on the completeness fraction, without introducing any biases. Our method produces results comparable to traditional methods at extremely low catalog completeness fractions (<0.5\%) or for very high uncertainties in the recovered luminosity distance and sky localization of the gravitational wave events.

astro-ph.CO↗

arXiv2026

Enhancing dark siren cosmology via Gaussian process reconstruction of incomplete galaxy catalogs

We present a novel framework for improving dark siren cosmology by applying a Gaussian process (GP) to the line-of-sight (LOS) reconstruction of incomplete galaxy catalogs. In the standard galaxy catalog method for inferring the Hubble constant $H_0$ from gravitational-wave (GW) dark sirens, missing galaxies are typically assumed to follow a uniform distribution in comoving volume, an assumption that discards galaxy redshift clustering information crucial for cosmological inference. We propose instead to model the LOS galaxy redshift distribution as a non-parametric function drawn from a GP realization, which is fitted to the observed incomplete catalog via a hierarchical Bayesian likelihood that explicitly accounts for the survey selection function. Applied to mock GW and galaxy catalogs extending up to redshift $z\leq0.4$, our method yields $H_0$ constraints that are on average 23% more precise than the standard homogeneous completion when using a 24%-complete galaxy catalog, and 37% more precise for an 8%-complete catalog. The largest improvement, reaching 66%, is obtained in configurations where the GP most effectively reconstructs the redshift over- and under-density features that the homogeneous completion fails to capture.

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arXiv2026

Pushing spectral siren cosmology into the third-generation era: a blinded mock data challenge

Gravitational wave (GW) spectral sirens offer a promising method for measuring cosmological parameters using GW data only - without relying on external redshift information such as electromagnetic counterparts or galaxy catalogs - by exploiting distributional features in the population of GW sources. The advent of third-generation detectors like the Einstein Telescope (ET) will provide catalogs three orders of magnitudes larger than current ones, raising questions about the scalability and robustness of existing inference pipelines. We present a blinded mock data challenge that tests three public pipelines with distinct numerical implementations, namely, $\texttt{ICAROGW}$, $\texttt{CHIMERA}$, and $\texttt{pymcpop-gw}$, on simulated ET observations containing the best $\mathcal{O}(10^4)$ binary black hole mergers that can be observed in 1 year. We assess their computational performance, validate their agreement in a blinded setting, and forecast cosmological constraints. We find that, thanks to GPU acceleration, these pipelines can process the events expected from ET within a manageable timeframe. All pipelines recover consistent cosmological and population parameters. Assuming a flat $\Lambda$CDM model, we measure $H(z)$ at $z\sim1.5$ with 2.4% precision, and achieve a mean precision on $H(z)$ of 2.8% across $0.7<z<1.8$ with a catalog of $\sim 12,000$ high-S/N events. This corresponds to joint constraints of $\sim 10%$ on $H_0$ and $\sim 26%$ on $\Omega_{\rm m,0}$. We also identify the events that contribute mostly to constraining cosmological parameters, showing that low-distance sources near population features drive the constraining power on all cosmological parameters, while higher-distance events primarily constrain $\Omega_{\rm m,0}$. Our results establish a validated, performance-tested framework for spectral siren cosmology in the era of third-generation GW observatories.

astro-ph.CO↗

arXiv2026

Probing Cosmic Expansion and Early Universe with Einstein Telescope

Over the next two decades, gravitational-wave (GW) observations are expected to evolve from a discovery-driven endeavour into a precision tool for astrophysics, cosmology, and fundamental physics. Current second-generation ground-based detectors have established the existence of compact-binary mergers and enabled GW multi-messenger astronomy, but they remain limited in sensitivity, redshift reach, frequency coverage, and duty cycle. These limitations prevent them from addressing many fundamental open questions in cosmology. By the 2040s, wide-field electromagnetic surveys will have mapped the luminous Universe with unprecedented depth and accuracy. Nevertheless, key problems including the nature of dark matter, the physical origin of cosmic acceleration, the properties of gravity on cosmological scales, and the physical conditions of the earliest moments after the Big Bang will remain only partially constrained by electromagnetic observations alone. Progress on these fronts requires access to physical processes and epochs that do not emit light. Gravitational waves provide a unique and complementary observational channel: they propagate over cosmological distances largely unaffected by intervening matter, probe extreme astrophysical environments, and respond directly to the geometry of spacetime. In this context, next-generation GW observatories such as the Einstein Telescope (ET) will be transformative for European astronomy. Operating at sensitivities and frequencies beyond existing detectors, ET will observe binary black holes and neutron stars out to previously inaccessible redshifts, enable continuous high signal-to-noise monitoring of compact sources, and detect gravitational-wave backgrounds of astrophysical and cosmological origin. Together with space-based detectors, ET will play a central role in advancing our understanding of cosmic evolution and fundamental physics.

astro-ph.CO↗

arXiv2026

Mind the peak: improving cosmological constraints from GWTC-4.0 spectral sirens using semiparametric mass models

Gravitational wave spectral sirens can provide cosmological constraints by using the shape of the binary black hole (BBH) mass distribution (MD). However, the precision and accuracy of these constraints depends critically on the capturing all the MD features. In this work, we analyze 137 BBH events from the latest GWTC-4.0 with a novel data-driven semiparametric approach based on \textsc{Bspline} that adaptively places knots around the most informative structures in the MD, while keeping the dimensionality of the parameter space moderate. Our flexible models resolve three distinct peaks at $\sim10$, $18$, and $33\,\mathrm{M}_\odot$ and are statistically preferred over standard parametric models, with Bayes factors up to 226. Because these features are correlated with $H_0$, the semiparametric model yields, under different prior assumptions, 12%-21% improvement in the precision of $H_0$ relative to parametric models, providing $H_0 = 57.8^{+21.9}_{-20.6}\,\mathrm{km/s/Mpc}$ in the best case. Our results demonstrate that capturing the full complexity of the BBH mass distribution is essential for realizing the cosmological potential of spectral sirens as gravitational wave catalogs continue to grow.

astro-ph.CO↗

arXiv2025

Echoes from the dark: Galaxy catalog incompleteness in standard siren cosmology

Gravitational wave observations can be combined with galaxy catalogs to constrain cosmology and test modified gravity theories using the standard siren method. However, galaxy catalogs are intrinsically incomplete due to observational limitations, potentially leaving host galaxies undetected, thereby weakening constraints and potentially introducing systematic errors. In this work, we present a self-consistent framework to study catalog incompleteness and host weighting effects, implemented in the publicly available CHIMERA pipeline. We obtain joint cosmological and astrophysical population constraints from 100 binary black hole (BBH) events in a LIGO-Virgo-KAGRA O5-like configuration using spectroscopic galaxy catalogs with varying completeness levels and stellar-mass host weighting schemes. We find percent-level constraints on $H_0$ with complete catalogs, reaching precisions of 1.6%, 1.3%, and 0.9% for constant, linear, and quadratic mass weighting, respectively. As completeness decreases, the precision degrades following a sigmoid trend, with a threshold and steepness that increase for stronger weightings. Simultaneously, the correlation between $H_0$ and the BBH population mass scale increases, making results more sensitive to assumptions about the astrophysical population. Remarkably, 2% precision remains achievable even when catalogs contain only 50% of the potential host galaxies within the gravitational wave detection horizon, while 1% precision requires host probabilities scaling with stellar mass squared. The results are robust against host weighting mismodeling, even at moderate completeness levels. This work further highlights the importance of spectroscopic galaxy surveys in standard siren cosmology and provides a pathway for developing the science case of future facilities.

astro-ph.CO↗

arXiv2025

Accelerating the standard siren method: Improved constraints on modified gravitational-wave propagation with future data

Gravitational waves (GWs) from compact binary mergers have emerged as one of the most promising probes of cosmology and General Relativity (GR). However, a major challenge in fully exploiting GWs as standard sirens with current and future GW observatories is developing efficient and robust codes capable of analyzing the increasing data volumes that are, and will be, acquired. We present here CHIMERA 2.0, an advanced computational framework for hierarchical Bayesian inference of cosmological, modified gravity, and population hyperparameters using standard sirens and galaxy catalogs. This upgrade introduces novel GPU-accelerated algorithms to estimate the hierarchical likelihood, enabling the analysis of thousands of events - crucial for next-generation experiments - and includes the two-parameter ($\Xi_0-n$) modified GW propagation model. Using CHIMERA 2.0, we forecast cosmological and modified GW propagation constraints for the future LIGO-Virgo-KAGRA O5-like run. We analyze three binary black hole populations of 300 events at SNR>20, each with a different value of $\Xi_0$: 0.6, 1 (corresponding to GR), and 1.8. Multiple analyses were performed each catalog, comprising a population of approximately 5000 events, thanks to CHIMERA 2.0, which is 10-1000 times faster depending on the settings and catalog size. We jointly infer cosmological, modified GW propagation, and population hyperparameters. With spectroscopic galaxy catalogs, the fiducial $\Xi_0$ is recovered with a precision of $22\%$, $7.5\%$, and $10\%$ for $\Xi_0$ = 0.6, 1, and 1.8, respectively; while the precision on $H_0$ is 2-7 times worse than when $\Xi_0$ is not inferred. Finally,in the case of photometric redshifts the constraints degrade on average by 3.5 times in all cases, underscoring the importance of future spectroscopic surveys in maximizing the constraining power of standard sirens.

astro-ph.CO↗

arXiv2025

Quest for CMB spectral distortions to probe the scalar-induced gravitational wave background interpretation of pulsar timing array data

Gravitational Waves (GW) sourced by second-order primordial curvature fluctuations are among the favored models fitting the recent pulsar timing array (PTA) measurement of a stochastic GW background (SGWB). We study how spectral distortions (SDs) and anisotropies of the cosmic microwave background (CMB) can constrain such scalar fluctuations. Whereas COBE FIRAS data have no sufficient sensitivity to probe the PTA log-normal hypothesis, we show how future PIXIE-like experiments can detect the CMB SDs from the scalar-induced interpretation of the SGWB in PTA data. We finally show how the transformative synergy between PTA data and future CMB SD measurements is important for reconstructing primordial fluctuations at these small scales.

astro-ph.CO↗

arXiv2024

Cosmology and Astrophysics with Standard Sirens and Galaxy Catalogs in View of Future Gravitational Wave Observations

With the growing number of gravitational-wave detections and the advent of large galaxy redshift surveys, a new era in cosmology is unfolding. This study explores the synergies between gravitational waves and galaxy surveys to jointly constrain cosmological and gravitational-wave population parameters. We introduce CHIMERA, a novel code for gravitational-wave cosmology combining information from the population properties of compact binary mergers and galaxy catalogs. We study constraints for scenarios representative of LIGO-Virgo-KAGRA O4 and O5 observing runs, assuming to have a complete catalog of potential host galaxies with either spectroscopic or photometric redshift measurements. We find that a percent-level measurement of $H_0$ could be achieved with the best 100 binary black holes in O5 using a spectroscopic galaxy catalog. In this case, the intrinsic correlation that exists between $H_0$ and the binary black hole population mass scales is broken. Instead, by using a photometric catalog the accuracy is degraded up to a factor of $\sim\! 9$, leaving a significant correlation between $H_0$ and the mass scales that must be carefully modeled to avoid bias. Interestingly, we find that using spectroscopic redshift measurements in the O4 configuration yields a better constraint on $H_0$ compared to the O5 configuration with photometric measurements. In view of the wealth of gravitational-wave data that will be available in the future, we argue the importance of obtaining spectroscopic galaxy catalogs to maximize the scientific return of gravitational-wave cosmology.

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