Publications

Title: Inferring astrophysics and cosmology with individual compact binary coalescences and their gravitational-wave stochastic background

Authors: S. Ferraiuolo, S. Mastrogiovanni, S. Escoffier, E. Kajfasz

Reference: arXiv:2503.14686

Content: 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.

Figure: Detectability of the SGWB during an O5-like run as a function of the Hubble constant. Lower values of the Hubble constant (older Universe) would result in a strong SGWB that, if not detected, would allow us to place limits on the Hubble constant.

Title: Investigating the impact of galaxies' compact binary hosting probability for gravitational wave cosmology

Authors: G. Perna, S. Mastrogiovanni, A. Ricciardone

Reference: arXiv:2405.07904, A&A 698, A128 (2025) 

Content: 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 emphasize the need for accurate modeling of host probabilities when combining GW data with galaxy catalogues.

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.

Title: Searching for additional structure and redshift evolution in the observed binary black hole population with a parametric time-dependent mass distribution

Authors: G. Vasco,  S. Mastrogiovanni, N. Tamanini, S. Marsat,  G. Pierra.

Reference: arXiv:2502.20445, Phys. Rev. D 111, 123046.

Content: 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.

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.

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

Reference: arXiv:2502.07675,  Class. Quantum Grav. 42 135016

Content: 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.

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).