arXiv subjects

Rodrigo Gonçalves

Publications and source records attributed to Rodrigo Gonçalves.

7 recordsLinked to original sources

arXiv2026

Testing Statistical Isotropy in the FRB Sky Distribution: A Selection-Function-Aware Framework

We perform a test of statistical isotropy in the Universe using the sky distribution of fast radio bursts (FRBs), based on a compilation of $4066$ events detected by multiple surveys. Our method is based on the two-point angular correlation function $w(θ)$ as in the Landy--Szalay estimator, together with a tomographic absolute-anisotropy statistic, and estimates their observational uncertainties from complementary jackknife and bootstrap resampling. Both estimators are confronted with hierarchical ensembles of isotropic mock catalogs that propagate the uncertainties of empirically reconstructed survey selection functions, as well as the Poisson fluctuations of the isotropic realizations. The significances are obtained from a covariance-aware, SVD-regularized $χ^2$ statistic calibrated empirically against the mock ensemble, and we evaluate four nested scenarios that progressively incorporate a Galactic-plane mask and the survey selection functions. As for our results, we find that the raw FRB sky is strongly inconsistent with isotropy; Galactic masking alone reduces the tension by only a factor of $\sim 3$, whereas the selection functions reduce it by nearly four orders of magnitude, showing that the apparent anisotropy is driven by the highly non-uniform sky coverage of the contributing surveys, overwhelmingly dominated by CHIME. Only when both effects are combined we obtain that the observed distribution is fully consistent with statistical isotropy. This result is independently corroborated by the absolute-anisotropy estimator, and is stable under variations of the analysis parameters. Therefore, we find that the FRB sky distribution is consistent with statistical isotropy, helping confirm one of the main predictions of the standard model scenario.

astro-ph.CO↗

arXiv2026

Cosmic homogeneity: the effect of redshift-space distortions and bias and cosmological constraints

We present a novel cosmological analysis based on the angular correlation dimension $D_2$ curve, a cumulative statistic derived from the two-point correlation function. Unlike traditional 3D approaches, angular $D_2$ is inherently less sensitive to nonlinear dynamical distortions, such as the small-scale Finger-of-God (FoG) effect. Using both MultiDark-Patchy and EZmock galaxy catalogs, we assess the scale-dependent impact of redshift-space distortions on $D_2$ and bias measurements. We demonstrate that the systematic errors associated with FoG modeling can be significantly reduced by restricting the analysis to appropriate minimum comoving angular scales of $\sim 1.25^{\circ} $, which corresponding to physical scales of $18$-$23\,h^{-1}\,\mathrm{Mpc}$ over the redshift range $0.46 \leq z \leq 0.74$ within the standard $Λ$CDM model. Since the observational estimative of $D_2(θ)$ is not dependent on a cosmological model we obtain robust estimates of the galaxy bias and place competitive constraints on the physical matter density $ω_m$. By applying this framework to SDSS DR12 and DR16 Luminous Red Galaxy data, we obtain $ω_m = 0.137^{+0.041}_{-0.059}$ (1$σ$), which agrees with current CMB analyses. Our results highlight the potential of the angular $D_2$ curve as a model-independent and robust tool for cosmological parameter inference.

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arXiv2026

The impact of FRB dispersion measure probability distribution functions on cosmographic estimates

Recent cosmological observations have reopened the discussion about the model that best describes the dynamics of the Universe, highlighting the need for cosmological model-independent analyses. In this paper, we utilize the cosmographic approach applied to a robust sample of 106 well-localized Fast Radio Bursts (FRBs) within the redshift range $z \le 0.7$ to constrain the Hubble constant $H_0$, the deceleration parameter $q_0$, and the jerk parameter $j_0$. Our primary goal is to assess the impact of intergalactic medium (IGM) inhomogeneities on cosmographic parameter estimation. To this end, we consider the statistical behavior of these parameters under two distinct functional forms for the IGM dispersion measure ($\mathrm{DM_{IGM}}$) probability density function (PDF): a Gaussian distribution (Distribution I) and a quasi-Gaussian distribution (Distribution II) that accounts for the skewed structure of cosmic large-scale environments along the lines of sight. We further investigate the role of the baryon mass fraction by considering both fixed and free-parameter scenarios. We find that the inferred cosmographic constraints, particularly those on $q_0$, depend sensitively on both the assumed IGM distribution and the adopted parameter priors.

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arXiv2026

Measurements of the Angular Homogeneity Scale from DESI DR1

The study of the large-scale distribution of galaxies provides essential information for testing the standard cosmological model, namely the $Λ$CDM paradigm. This scenario is based upon two foundations: General Relativity as the theory of gravity, and the Cosmological Principle, which states that the Universe is statistically homogeneous and isotropic on large scales -- so that we can measure distances and ages in the Universe assuming the FLRW metric. In this work, we perform a test of the Cosmological Principle by probing the angular homogeneity scale, $θ_H$, using the state-of-the-art observational data of Luminous Red Galaxies (LRGs) from the Dark Energy Spectroscopic Instrument Data Release 1 (DESI DR1). Our analysis is performed exclusively in two dimensions, across narrow redshift ranges inside a larger redshift sample of $0.4 < z < 1.1$, in two different surveyed regions of the sky (North and South Galactic Caps), as we want to minimize a priori dependences on an underlying cosmological model. We obtain that such a scale is indeed identified in all redshift ranges, and that they are consistent with mock simulations assuming the $Λ$CDM model. Moreover, our results are in great agreement with previous measurements using Sloan Digital Sky Survey IV extended Baryon Oscillation Spectroscopic Survey Data Release 16 (SDSS-IV eBOSS DR16), as well as between the north and south galactic caps of the DESI DR1 survey. These findings help underpinning statistical isotropy and homogeneity of the Universe as a physically valid hypothesis in light of upcoming stage-IV redshift surveys, hence are consistent with one of the fundamental pillars of the standard cosmological model.

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arXiv2026

Cosmographic parameters from current and next-generation gravitational wave detectors

We evaluate the capability of current and next-generation gravitational wave detectors, such as Advanced LIGO, Einstein Telescope and DECIGO, to constrain cosmographic parameters using electromagnetically bright standard sirens. By adopting a third-order Taylor expansion, we analyze how signal-to-noise ratios and the number of events impact the estimates of the Hubble constant ($H_0$), the deceleration ($q_0$) and jerk ($j_0$) parameters. Our results show that while Advanced LIGO provides a calibration-free measurement of $H_0$ at the few-percent level, it remains insensitive to higher-order parameters. In contrast, the Einstein Telescope and DECIGO reach sub-percent accuracy for $H_0$. Notably, DECIGO achieves a precision better than 10\% for the deceleration parameter $q_0$ and a few tens of percent for the jerk parameter $j_0$.

astro-ph.CO↗

arXiv2025

Cosmological-model independent limits on photon mass from FRB and SNe data

Electromagnetic emissions from astrophysical sources at cosmological distances can be used to estimate the photon mass, $m_γ$. In this paper, we combine measurements of the dispersion measure ($\mathrm{DM}$) of fast radio bursts (FRB) with the luminosity distance from type Ia supernovae (SNe) to investigate update constraints on the photon rest mass. We derive the expression of $\mathrm{DM}$ dependence concerning a non-vanishing photon mass from a cosmological-model independent approach and constrain the parameter $m_γ$ from measurements of 68 well-localized FRBs and 1048 SNe data from the Pantheon compilation. We consider two scenarios for the baryon fraction in the intergalactic medium ($f_{\mathrm{IGM}}$): one where the value is fixed according to recent reports and another where it is treated as a free parameter, $f_{\mathrm{IGM}} = f_{\mathrm{IGM,0}}$. In the latter case, we find $m_γ = (29.4_{-15.5}^{+5.80}) \times 10^{-51}$ kg, at $1σ$ level. Our results also demonstrate an anticorrelation between $f_{\mathrm{IGM}}$ and $m_γ$, which highlights the importance of analyzing a larger sample of FRBs for a more comprehensive understanding of their properties.

astro-ph.CO↗

arXiv2025

A search for the fine-structure constant evolution from fast radio bursts and type Ia supernovae data

The search for a space-time variation of the fundamental constants has been explored over the years to test our physical theories. In this paper, we use the dispersion measure ($DM$) of fast radio bursts (FRB) combined with type Ia supernovae (SNe) data to investigate a possible redshift evolution of the fine-structure constant ($α$), considering the runaway dilaton scenario, which predicts $\frac{Δα}α = - γ\ln{(1+z)}$, where $γ$ is a constant proportional to the current value of the coupling between the dilaton field and hadronic matter. We derive all the relevant expressions for the $DM$ dependence concerning the fine-structure constant and constrain the parameter $γ$ from measurements of 17 well-localized FRBs and 1048 SNe data from the Pantheon compilation. We also use Monte Carlo simulations to forecast the constraining power of larger samples of FRB measurements for data sets with $N = 500$ and $N = 1000$ points. We found that the uncertainty on $γ$ can be improved by one order of magnitude and that limits on $\frac{Δα}α$ beyond $σ\sim 10^{-2}$ will depend crucially on better control of statistical and systematic uncertainties of upcoming FRB data.

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