arXiv subjects

F. Avila

Publications and source records attributed to F. Avila.

6 recordsLinked to original sources

arXiv2025

A cosmology weakly dependent measurement of 2D Baryon Acoustic Oscillations scale from the Southern Photometric Local Universe Survey

Baryon Acoustic Oscillations (BAO) provide a robust standard ruler for observational cosmology, enabling precise constraints on the expansion history of the Universe. We present a weakly model-dependent measurement of the BAO angular scale in the low-redshift Universe using the blue galaxies from the Southern Photometric Local Universe Survey (S-PLUS). Our analysis is based on the 2-point angular correlation function applied to a selected photometric sample of $5977$ galaxies with redshifts $0.03 \leq z \leq 0.1$. To account for photometric redshift uncertainties, we implement a resampling technique using the probability distribution function of each galaxy. Angular correlations are computed using the Landy-Szalay estimator; the uncertainties are quantified using a set of $1000$ log-normal mock catalogues. Our 2-point angular correlation analyses reveal a prominent BAO signal that after a shift correction, due to the projection effect caused by the finite thickness of the redshift bin, provides the transversal BAO measurement: $\theta_{BAO} = 21.81^{\circ} \pm 0.85^{\circ}$, at $z_{eff} = 0.075$, detected with a statistical significance of $3.22 \sigma$. In addition, we performed consistency tests that support the robustness of our result. Our measurement constitutes the first robust detection of the transversal BAO scale: at the lowest-redshift in the Universe and using multi-band (narrow+wide) photometry data from the S-PLUS.

astro-ph.CO↗

arXiv2021

The growth rate of cosmic structures in the local Universe with the ALFALFA survey

We investigate the growth rate of structures in the local Universe. For this, we use as a cosmological tracer the HI line extra-galactic sources from the Arecibo Legacy Fast ALFA (ALFALFA) survey to obtain a measurement of the normalized growth rate parameter, $f \sigma_{8}$, considered a powerful tool to constrain alternative models of gravity. For these analyses, we calculate the Local Group velocity due to the matter structures distribution in the ALFALFA catalogue and compare it with the Local Group velocity relative to the Cosmic Microwave Background frame to obtain the velocity scale parameter, $\beta$. Using Monte Carlo realizations and log-normal simulations, our methodology quantifies the errors introduced by shot-noise and partial sky coverage of the analysed data. The measurement of the velocity scale parameter $\beta$, and the calculation of the matter fluctuation of the cosmological tracer, $\sigma_{8}^{\text{tr}}$, lead us to $f \sigma_{8} = 0.46 \pm 0.06$ at $\bar{z} = 0.013$, in good agreement (at $1 \sigma$ level) with the value expected in the $\Lambda$CDM concordance model. In addition, our analyses of the ALFALFA sample also provide a measurement of the growth rate of structures $f \,=\, 0.56 \pm 0.07$, at $\bar{z} = 0.013$.

astro-ph.CO↗

arXiv2021

BAO angular scale at z_eff = 0.11 with the SDSS blue galaxies

We measure the transverse baryon acoustic oscillations (BAO) signal in the local Universe using a sample of blue galaxies from the Sloan Digital Sky Survey (SDSS) survey as a cosmological tracer. The method is weakly dependent on a cosmological model and is suitable for 2D analyses in thin redshift bins to investigate the SDSS data in the interval $z {\in} [0.105, 0.115]$. We detect the transverse BAO signal ${\theta}_{BAO} = 19.8^{\deg} {\pm} 1.05^{\deg}$ at $z_{eff} = 0.11$, with a statistical significance of $2.2 {\sigma}$. Additionally, we perform tests that confirm the robustness of this angular BAO signature. Supported by a large set of log-normal simulations, our error analyses include statistical and systematic contributions. In addition, considering the sound horizon scale calculated by the Planck Collaboration, $r_{s}^{Planck}$, and the ${\theta}_{BAO}$ value obtained here, we obtain a measurement of the angular diameter distance $D_{A}(0.11) = 258.31 {\pm} 13.71 \,Mpc/h$. Moreover, combining this ${\theta}_{BAO}$ measurement at low redshift with other BAO angular scale data reported in the literature, we perform statistical analyses for the cosmological parameters of some Lambda cold dark matter (${\Lambda}$CDM) type models.

astro-ph.CO↗

arXiv2019

The angular scale of homogeneity in the Local Universe with the SDSS blue galaxies

We probe the angular scale of homogeneity in the local Universe using blue galaxies from the SDSS survey as a cosmological tracer. Through the scaled counts in spherical caps, $ \mathcal{N}(<θ) $, and the fractal correlation dimension, $\mathcal{D}_{2}(θ)$, we find an angular scale of transition to homogeneity for this sample of $θ_{\text{H}} = 22.19^{\circ} \pm 1.02^{\circ}$. A comparison of this measurement with another obtained using a different cosmic tracer at a similar redshift range ($z < 0.06$), namely, the HI extragalactic sources from the ALFALFA catalogue, confirms that both results are in excellent agreement (taking into account the corresponding bias correction). We also perform tests to asses the robustness of our results. For instance, we test if the size of the surveyed area is large enough to identify the transition scale we search for, and also we investigate a reduced sample of blue galaxies, obtaining in both cases a similar angular scale for the transition to homogeneity. Our results, besides confirming the existence of an angular scale of transition to homogeneity in different cosmic tracers present in the local Universe, show that the observed angular scale $θ_{\text{H}}$ agrees well with what is expected in the $Λ$CDM scenario. Although we can not prove spatial homogeneity within the approach followed, our results provide one more evidence of it, strengthening the validity of the Cosmological Principle.

astro-ph.CO↗

arXiv2018

The scale of homogeneity in the local Universe with the ALFALFA catalogue

We use the scaled counts in spherical caps $\mathcal{N}(<θ)$ and the fractal correlation dimension $ \mathcal{D}_{2}(θ) $ procedures to search for a transition scale to homogeneity in the local universe as given by the ALFALFA catalogue (a sample of extragalactic HI line sources, in the redshift range $0 < z < 0.06$). Our analyses, in the 2-dimensional sky projected data, show a transition to homogeneity at $θ_H = 16.49^{\circ} \pm 0.29^{\circ}$, in remarkable accordance with the angular scale expected from simulations, a result that strengthens the validity of the cosmological principle in the local universe. We test the robustness of our results by analysing the data sample using three versions of the $\mathcal{N}(<θ)$ estimator, which show a well agreement between them. These statistical estimators were validated using mock realizations generated assuming a fractal distribution of points, successfully recovering the input information. In addition, we perform further analyses showing that our approach is also able to indicate the presence of under- and over-densities in the data. Finally, we verify the influence of the sample size to the $θ_H$ estimates by using segment Cox processes of different projected areas, confirming the suitability of the ALFALFA surveyed area for the current analyses.

astro-ph.CO↗

arXiv2016

Night sky brightness at San Pedro Martir Observatory

We present optical UBVRI zenith night sky brightness measurements collected on eighteen nights during 2013--2016 and SQM measurements obtained daily over twenty months during 2014--2016 at the Observatorio Astronomico Nacional on the Sierra San Pedro Martir (OAN-SPM) in Mexico. The UBVRI data is based upon CCD images obtained with the 0.84m and 2.12m telescopes, while the SQM data is obtained with a high-sensitivity, low-cost photometer. The typical moonless night sky brightness at zenith averaged over the whole period is U = 22.68, B = 23.10, V = 21.84, R = 21.04, I = 19.36, and SQM = 21.88 mag/square arcsec, once corrected for zodiacal light. We find no seasonal variation of the night sky brightness measured with the SQM. The typical night sky brightness values found at OAN-SPM are similar to those reported for other astronomical dark sites at a similar phase of the solar cycle. We find a trend of decreasing night sky brightness with decreasing solar activity during period of the observations. This trend implies that the sky has become darker by delta_U =0.7, delta_B =0.5, delta_V =0.3, delta_R =0.5 mag/square arcsec since early 2014 due to the present solar cycle.

astro-ph.IM↗