PhD student Gabriele Perna, now a Postdoc,

Our research explores how future gravitational wave (GW) observations—especially those without electromagnetic counterparts—can still be used to infer key cosmological parameters like the Hubble constant (H₀). We investigate how incorrect assumptions about the GW host galaxy distribution, particularly regarding luminosity and redshift, can bias H₀ measurements. Using realistic galaxy and compact binary coalescence simulations, we show that such biases depend on both the observational footprint and distance of GW events. Our findings emphasise the need for accurate modelling of host probabilities when combining GW data with galaxy catalogues.

Please, feel free to read our paper and reach out to us for any question or suggestion.

Figure: Hubble constant posterior calculated using 200 well-localised dark sirens when assuming different models for the galaxies’ hosting probability of binary black holes. The true underlying astrophysical population is generated with the model indicated on the top left panel.

PhD student Sarah Ferraiuolo presented a new study on how the stochastic gravitational-wave background can improve the measures of the Hubble parameter.

The individual gravitationa-wave (GW) sources that we see in our detectors are just the tip of the iceberg. Below them, thousands of silent GW sources compose the stochastic GW background (SGWB). In this paper, we demonstrate that the SGWB can be exploited, along with resolved sources,  to measure cosmological expansion parameters.  Its inclusion can help us to constrain cosmological models where the Universe is very old.

Please, feel free to read our paper and reach out to us for any question or suggestion.

Figure: Hubble parameter reconstructed from only resolved GW sources (pink) and with the stochastic GW background (blue).

PhD student Vasco Gennari led an amazing work where we delved into the secrets of the impact of parametric models for the source mass of binary black holes in GW cosmology.

We present an extensive study on how different parameterizations of the source frame mass spectrum of binary black holes (BBHs) impact the population studies of detected sources. We find that for mass models that are non-evoling in redshift and only model one sharp feature in the mass spectrum, the mass spectrum reconstruction from real data is population prior-dependent. We demonstrate that this can happen when real data contains more than one feature. We also studied a set of parametric models evolving in redshift and found no strong preference against redshift-independent models.

Please, feel free to read our paper and reach out to us for any question or suggestion.

Figure: Reconstruction of the astrophysical (top panel) and detected (bottom panel) mass spectrum for two population models with multiple features. Two different models could not be distinguishable as at the detector they would correspond to the same distribution.

With Elisa Maggio and Adriano Frattale-Mascioli we looked at the detected gravitational waves populations as if composed of exotic compact objects.

Exotic compact objects (ECOs) are proposed alternatives to black holes (BHs) that can mimic their behaviours while removing the event horizon. However, ECOs are subject to ergoregion instability; namely, if their spin is too high, they are unstable. We infer that no more than 20% of the compact objects could be ECOs by looking at the spin distribution of detected GW sources. We also demonstrate that the Einstein Telescope will obtain far better results with just a few days of data-taking.

Please, feel free to read our paper and reach out to us for any question or suggestion.

Title: Limits on the existence of totally reflective exotic compact objects with current and future gravitational-wave detectors

Authors: S. Mastrogiovanni, E. Maggio, A. Frattale-Mascioli

Figure: Upper limits on the fraction of ECOs as function of the compactness (position of the ECO’s surface from the would-be event horizon).

Myself and Prof. Antonella Palmese recently drafted a 2025 review of gravitational wave cosmology.

It is a gentle introduction and review to standard sirens cosmology is a contribution to the Encyclopedia of Astrophysics (edited by Springer). The review covers in details methods for gravitational-wave cosmology with the mass spectrum, galaxy catalogs and electromagnetic counterparts.

Please, feel free to read our paper and reach out to us for any question or suggestion.

Figure: Depiction of the source mass method to infer the Hubble constant.

Leonardo Iampieri presented a new paper where we develop a novel strategy to study cosmic expansion with Gravitational Wave (GW) sources without an identified host galaxy but with an associated electromagnetic (EM) counterpart. We show that the relative time delay between the GW luminosity peak and the arrival of the EM counterpart can be used to measure the cosmic expansion and also fit the distribution of gamma-ray bursts prompt time delays.

Please, feel free to read our paper and reach out to us for any question or suggestion.

Figure: Posterior on the Hubble constant and mean and standard deviation of the GW-GRB prompt time delay distribution with 100 binary neutron star events.