arXiv subjects

Gabriela C. Carvalho

Publications and source records attributed to Gabriela C. Carvalho.

6 recordsLinked to original sources

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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arXiv2025

Cosmological constraints from angular homogeneity scale measurements

In this paper, we obtain new measurements of the angular homogeneity scale ($θ_H$) from the BOSS DR12 and eBOSS DR16 catalogs of Luminous Red Galaxies of the Sloan Digital Sky Survey. Considering the flat $Λ$CDM model, we use the $θ_H(z)$ data to constrain the matter density parameter ($Ω_{m0}$) and the Hubble constant ($H_{0}$). We find $H_0 = 65^{+10}_{-7}$ km s$^{-1}$ Mpc$^{-1}$ and $Ω_{m0}>0.296$. By combining the $θ_H$ measurements with current Baryon Acoustic Oscillations (BAO) and Type Ia Supernova (SN) data, we obtain $H_{0}= 66.8 \pm 5.0$ km s$^{-1}$ Mpc$^{-1}$ and $Ω_{m0} = 0.292^{+0.013}_{-0.015}$ ($θ_H$ + BAO) and $H_{0}=66.8 \pm 5.4 $ km s$^{-1}$ Mpc$^{-1}$ and $Ω_{m0}=0.331 \pm 0.018$ ($θ_H$ + SN). We show that $θ_H$ measurements help break the BAO and SN degeneracies concerning $H_0$, as they do not depend on the sound horizon scale at the drag epoch or the SN absolute magnitude value obtained from the distance ladder method. Hence, despite those constraints are less stringent compared to other probes, $θ_H$ data may provide an independent cosmological probe of $H_0$ in light of the Hubble tension. For completeness, we also forecast the constraining power of future $θ_H$ data via Monte Carlo simulations. Considering a relative error of the order of 1$\%$, we obtain competitive constraints on $Ω_{m0}$ and $H_0$ ($\approx 5\%$ error) from the joint analysis with current SN and BAO measurements.

astro-ph.CO↗

arXiv2024

Can the angular scale of cosmic homogeneity be used as a cosmological test?

In standard cosmology, the cosmic homogeneity scale is the transition scale above which the patterns arising from non-uniformities -- such as groups and clusters of galaxies, voids, and filaments -- become indistinguishable from a random distribution of sources. Recently, different groups have investigated the feasibility of using such a scale as a cosmological test and arrived at different conclusions. In this paper, we complement and extend these studies by exploring the evolution of the spatial (${\cal{R}}_H$) and angular ($θ_H$) homogeneity scales with redshift, assuming a spatially flat, $Λ$-Cold Dark Matter %($Λ$CDM) universe and linear cosmological perturbation theory. We confirm previous results concerning the non-monotonicity of ${\cal{R}}_H$ with the matter density parameter $Ω_{m0}$ but also show that it exhibits a monotonical behavior with the Hubble constant $H_0$ within a large redshift interval. More importantly, we find that, for $z \gtrsim 0.6$, the angular homogeneity scale not only presents a monotonical behavior with $Ω_{m0}$ and $H_0$ but is quite sensitive to $H_0$, especially at higher redshifts. These results, therefore, raise the possibility of using $θ_H$ as a new, model-independent way to constrain cosmological parameters.

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arXiv2022

The angular scale of homogeneity with SDSS-IV DR16 Luminous Red Galaxies

We report measurements of the angular scale of cosmic homogeneity ($θ_{H}$) using the recently released luminous red galaxy sample of the sixteenth data release of the Sloan Digital Sky Survey (SDSS-IV LRG DR16). It consists of a model-independent method, as we only use the celestial coordinates of these objects to carry out such an analysis. The observational data is divided into thin redshift bins, namely $0.67<z<0.68$, $0.70<z<0.71$, and $0.73<z<0.74$, in order to avoid projection biases, and we estimate our uncertainties through a bootstrap method and a suite of mock catalogues. We find that the LRGs exhibit an angular scale of homogeneity consistent with the predictions of the standard cosmology within the redshift interval studied. Considering the bootstrap method, in which the measurements are obtained in a model-independent way, we found at 1$σ$ level that $θ_H^{boot}(0.675) = 7.57 \pm 2.91$ deg, $θ_H^{boot} (0.705) = 7.49 \pm 2.63$ deg and $θ_H^{boot} (0.735) = 8.88 \pm 2.81$ deg. Such results are in good agreement with the ones obtained using mock catalogues built under the assumption of the standard cosmological model.

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arXiv2021

Measuring the cosmic homogeneity scale with SDSS-IV DR16 Quasars

We report measurements of the scale of cosmic homogeneity ($r_{h}$) using the recently released quasar sample of the sixteenth data release of the Sloan Digital Sky Survey (SDSS-IV DR16). We perform our analysis in 2 redshift bins lying in the redshift interval $2.2 < z < 3.2$ by means of the fractal dimension $D_2$. By adopting the usual assumption that $r_{h}$ is obtained when $D_2 \sim 2.97$, that is, within 1% of $D_2=3$, we find the cosmic homogeneity scale with a decreasing trend with redshift, and in good agreement with the $Λ$CDM prediction. Our results confirm the presence of a homogeneity scale in the spatial distribution of quasars as predicted by the fundamental assumptions of the standard cosmological model.

astro-ph.CO↗

arXiv2016

Measuring baryon acoustic oscillations with angular two-point correlation function

The Baryon Acoustic Oscillations (BAO) imprinted a characteristic correlation length in the large-scale structure of the universe that can be used as a standard ruler for mapping out the cosmic expansion history. Here, we discuss the application of the angular two-point correlation function, $w(θ)$, to a sample of luminous red galaxies of the Sloan Digital Sky Survey (SDSS) and derive two new measurements of the BAO angular scale at $z = 0.235$ and $z = 0.365$. Since noise and systematics may hinder the identification of the BAO signature in the $w - θ$ plane, we also introduce a potential new method to localize the acoustic bump in a model-independent way. We use these new measurements along with previous data to constrain cosmological parameters of dark energy models and to derive a new estimate of the acoustic scale $r_s$.

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