Abstract
The concordance cosmological model: stress-tests with galaxy clusters. " We propose to address the tensions related to the measurements of the present value of Hubble constant H0 and of the galaxy cluster masses with a multi-wavelength homogenous joint analysis of these ultimate products of structure formation in time and mass. By assessing their mass scale, their mass distribution, the shapes of the hosting haloes and their distances (by combining X-ray and Sunyaev-Zeldovich signals), their number density and clustering with unique samples, we plan to constrain the most fundamental parameters describing the constituents of our Universe in the framework of the concordance cosmological Lambda Cold Dark Matter model, and we will quantify any tension within the current paradigm. " "The main goals of the project are: 1. Reconstruction of the pressure profile in the CHEX-MATE cluster sample for a precise and robust estimate of the thermodynamic quantities (both spatially resolved and integrated) and of the hydrostatic mass. Measurements of the weak-lensing masses, putting exquisite constraints on the hydrostatic bias. 2. Constraints on the triaxial shape of the distribution of both the gas and the dark matter. How the dark mass is concentrated and distributed, what is the gas mass fraction and how the gravitational acceleration manifests itself on different scales are all quantities influenced by cosmology, and therefore they provide incisive cosmological tests. 3. The knowledge of the triaxial shape and the independent measurements of the different dependence on the scale of the electron density from X-ray and SZ data will provide a unique estimate of H0. 4. The calibration of the scaling laws between weak-lensing masses and optical richness, among others, will allow us to convert the measurements of the number counts and clustering in the KiDS catalogs into powerful cosmological constraints."
Results achieved
: KiDS We extended our cosmological analysis of the DR3 release of KiDS by studying the tomographic clustering properties in Romanello et al. (2024), where we focused on the angular correlation function and the angular power spectrum. We obtained Ωm=0.32±0.05, σ8=0.77±0.11, and S8= 0.80±0.07, in agreement, within 1σ, with the 3D clustering result based on the same cluster sample. Considering the angular power spectrum, we derived statistically consistent results, in particular, Ωm=0.24±0.05 and S8=0.93±0.12, while the constraint on σ8 alone is weaker with respect to the one provided by the angular correlation function, σ8=1.01±0.23. This work on real data has been prepared by a preliminary comparative study between 3D and 2D tomographic clustering performed on simulated data (Romanello et al. 2025). We used the AMICO-DR3 cluster sample to model the splashback radius (Giocoli et al. 2024). Employing a comprehensive Bayesian analysis, we described the stacked excess surface mass density distribution of the clusters adopting a model from recent results on numerical simulations that capture the dynamics of both orbiting and infalling materials. We found that the adopted profile successfully characterises the cluster masses and models the deepening of the slope of the density profiles measured with weak-lensing data up to the outskirts. Moreover, we measured the splashback radius of galaxy clusters and show that its value is close to R200. We presented a new catalogue of galaxy clusters detected in KiDS-DR4 optimised for cosmological analyses and investigations of cluster properties (Maturi et al. 2025). Each detection includes probabilistic membership assignments for the KiDS-DR4 galaxies within the magnitude range 15<24. Using the AMICO algorithm, we identified 23965 clusters over an area of 839 deg2 in the range 0.1≤z≤ 0.9, with S/N >3.5. We derived a mass-proxy scaling relation based on intrinsic richness using masses from the eRASS1 catalogue. A subsample of about 8000 clusters extracted from this catalogue has been used for deriving cosmological constraints from the joint modelling of weak-lensing and count measurements (Lesci et al. 2025). Stacked cluster weak-lensing and count measurements have been derived in bins of redshift and intrinsic richness. We accounted for the systematic uncertainties arising from impurities in the background and cluster samples, biases in the cluster redshift and richness, projection effects, halo orientation and miscentring, truncation of cluster halo mass distributions, matter correlated with cluster haloes, multiplicative shear bias, baryonic matter, geometric distortions in the lensing profiles, uncertainties in the theoretical halo mass function, and super-sample covariance. The improved statistics and photometry compared to KiDS-DR3 have led to a halving of the uncertainties on Ωm and σ8: Ωm=0.22±0.02 and σ8=0.86±0.03. The constraint on S8=0.74±0.03 is in excellent agreement with recent cluster count and KiDS-1000 cosmic shear analyses, while it shows a 2.8σ tension with Planck CMB results. Numerical Simulations Using simulations with dark matter only and with a full-physics set-up including a self-consistent treatment of baryon physics we assessed the impact of dark matter self-interactions on the properties of galaxy clusters (Ragagnin et al. 2024), analysing their matter density profiles as well as their subhalo population. We found that our dark matter-only SIDM simulations agree with theoretical models, and when baryons are included in simulations, our SIDM models substantially increase the central density of galaxy cluster cores compared to full-physics simulations using collisionless dark matter. SIDM subhalo suppression in full-physics simulations is milder compared to the one found in the dark matter-only simulations because of the cuspier baryonic potential that prevents subhalo disruption. We used the state-of-the-art hydro simulations of galaxy clusters carried out with GadgetX and GIZMO-SIMBA as part of the Three Hundred project to investigate the effect of the presence of baryons on the weak-lensing mass bias and whether this bias depends on the galaxy formation recipe (Giocoli et al. 2025). We derived the weak-lensing mass-richness relation and found consistency within 1σ uncertainties across hydro simulations. The intercept parameter of the relation is independent of redshift but varies with the minimum of the stellar mass used to define the richness value. The scatter in observed richness at a fixed weak-lensing mass increases linearly with redshift at a fixed stellar mass cut. We introduced the AIDA-TNG project, a suite of cosmological magnetohydro simulations that simultaneously model galaxy formation and different variations in the underlying dark matter model (Despali et al. 2025). The simulations adopt the fiducial IllustrisTNG galaxy formation model and consider the standard CDM model and five variations, including three warm dark matter scenarios and two self-interacting models with a constant or velocity-dependent cross-section. We presented the first results on statistical quantities such as the halo mass function and the matter power spectrum quantifying the modification in the number of haloes and the power on scales smaller than 1 Mpc due to the combination of baryonic and dark matter physics. Finally, we also quantified changes in halo structure due to warm and self-interacting dark matter, which appear in the density profiles, concentration-mass relation, and galaxy sizes. Cluster detection We performed a new galaxy cluster search in the COSMOS field using the AMICO algorithm (Toni et al. 2024). Our aim was to produce a new cluster and group catalogue up to z=2 by performing an innovative application of AMICO with respect to previous successful applications to wide-field surveys in terms of depth (down to r < 26.7), small area covered (∼1.69 deg2), and redshift extent. We used three different magnitudes by performing three independent runs in the r-, Y-, and H-bands. We performed a matching of the catalogues resulting from the three runs and merged them to produce a final catalogue that contains 1269 candidate clusters and groups with S/N>3.0. We assigned X-ray properties to our detections by matching the catalogue with a public X-ray selected group sample and by estimating, for unmatched detections, the X-ray properties at the location of AMICO candidates. There are in total 622 candidate clusters and groups with an X-ray flux estimate. This large sample of candidates with X-ray properties allowed the calibration of the scaling relations between the AMICO mass-proxies and X-ray mass. By leveraging the deep imaging, high resolution, and high-quality photometry from the JWST observations of the COSMOS-Web field, we built the largest deep catalogue of galaxy groups to date over an effective area of 0.45 deg2 applying the AMICO algorithm (Toni et al. 2025a). We detected 1678 groups up to z=3.7 with a purity level of ∼77%, providing a deep catalogue of galaxy members that extends nearly two magnitudes deeper than the previous application of AMICO to COSMOS. Around 670 groups have been detected with a purity of 90%. We also compiled a list of known protoclusters in COSMOS at 2≤z≤3.7 and matched them with our detections. We introduced AMICO-WL, an extension of the optimal filtering algorithm implemented in AMICO. AMICO-WL adopt a specific linear optimal matched filter for weak lensing data in the AMICO infrastructure, using parallelisation and adding an efficient signal-to-noise ratio thresholding approach to set a desired sample purity and a cleaning procedure to deal with blended detections. We implemented a foreground removal procedure based on different cuts of low redshift galaxies from the input catalogue.Project details
Unibo Team Leader: Lauro Moscardini
Unibo involved Department/s:
Dipartimento di Fisica e Astronomia "Augusto Righi"
Coordinator:
Inaf - Istituto Nazionale Astrofisica(Italy)
Total Unibo Contribution: Euro (EUR) 71.501,00
Project Duration in months: 24
Start Date:
28/09/2023
End Date:
27/09/2025
