arXiv subjects

Marcelo Ferreira

Publications and source records attributed to Marcelo Ferreira.

4 recordsLinked to original sources

arXiv2026

Investigating a Possible Variation of the Gravitational Constant Through Gas Mass Fraction Measurements and Type Ia Supernovae Observations

In this paper, we investigate a possible time variation of the gravitational constant (G) using a non-parametric approach. Our main cosmological probe is the gas mass fraction of galaxy clusters measured from X-ray observations. We also account for the effect of a varying $G$ on the intrinsic luminosity of type Ia supernovae (SNe Ia) through the Chandrasekhar mass-luminosity relation. We consider a specific phenomenological scenario, motivated by some scalar-tensor and screened modified-gravity frameworks, in which the standardized luminosity of SNe Ia decreases with increasing Chandrasekhar mass. Using gas mass fraction measurements jointly with luminosity distances from the Pantheon+ compilation, we reconstruct the evolution of G through Gaussian Processes. Our results indicate that a constant gravitational coupling remains broadly consistent with the data, although mild low-redshift departures are allowed.

astro-ph.CO↗

arXiv2026

Revisiting the Constancy of the Speed of Light: Galaxy Cluster Mass Bias Implications

In recent years, improvements in galaxy cluster observations have enabled a variety of tests of fundamental physics using these systems. In this work, we test the constancy of the speed of light, $c$, by combining X-ray gas mass fraction measurements from galaxy clusters with SNe Ia luminosity distance measurements from Pantheon+. We adopt the SH0ES prior on $H_0$ and the $Ω_b/Ω_m$ ratio from galaxy clustering observations, thereby minimizing the dependence of our analysis on any specific cosmological model. We explore different assumptions for the cluster mass calibration (mass bias), including \textsc{CLASH}, \textsc{CCCP}, and Planck-based estimates. We find no deviation from a constant $c$ when adopting \textsc{CLASH} or \textsc{CCCP} priors, while Planck-based calibration yields a mild tension, with the hypothesis of constant $c$ being only marginally consistent at the $2σ$ level, indicating a non-negligible sensitivity of the results to the adopted calibration scheme.

astro-ph.CO↗

arXiv2024

Non-parametric reconstruction of the fine structure constant with galaxy clusters

Testing possible variations in fundamental constants of nature is a crucial endeavor in observational cosmology. This paper investigates potential cosmological variations in the fine structure constant ($α$) through a non-parametric approach, using galaxy cluster observations as the primary cosmological probe. We employ two methodologies based on galaxy cluster gas mass fraction measurements derived from X-ray and Sunyaev-Zeldovich observations, along with luminosity distances from type Ia supernovae. We also explore how different values of the Hubble constant ($H_0$) impact the variation of $α$ across cosmic history. When using the Planck satellite's $H_0$ observations, a constant $α$ is ruled out at approximately the 3$σ$ confidence level for $z \lesssim 0.5$. Conversely, employing local estimates of $H_0$ restores agreement with a constant $α$.

astro-ph.CO↗

arXiv2024

Unveiling the Hubble Constant through Galaxy Cluster Gas Mass Fractions

In this work, we obtain Hubble constant ($H_0$) estimates by using two galaxy cluster gas mass fraction measurement samples, Type Ia supernovae luminosity distances, and the validity of the cosmic distance duality relation. Notably, the angular diameter distance (ADD) to each galaxy cluster in the samples is determined by combining its gas mass fraction measurement with galaxy clustering observations, more precisely, the $Ω_b/Ω_m$ ratio. Such a combination results in a $H_0$ estimate that is independent of a specific cosmological framework. In one of the samples, the gas fraction measurements were calculated in spherical shells at radii near $r_{\rm 2500}$ (44 data points), while in the other (103 data points) the measurements were calculated within $ r_{\rm 500}$. We find $H_0=72.7^{+6.3}_{-5.6}$ km/s/Mpc at 68\% CL for the joint analysis of these data sets. We also investigate the impact on the $H_0$ determination by exploring the precision and number of gas mass fraction data by performing a data Monte Carlo simulation. Our simulations show that future measurements could achieve a precision of up to 5\% for $H_0$.

astro-ph.CO↗