arXiv subjects

Rigoberto A. Casas-Miranda

Publications and source records attributed to Rigoberto A. Casas-Miranda.

4 recordsLinked to original sources

arXiv2020

Validating the methodology for constraining the linear growth rate from clustering anisotropies

Redshift-space clustering distortions provide one of the most powerful probes to test the gravity theory on the largest cosmological scales. We perform a systematic validation study of the state-of-the-art statistical methods currently used to constrain the linear growth rate from redshift-space distortions in the galaxy two-point correlation function. The numerical pipelines are tested on mock halo catalogues extracted from large N-body simulations of the standard cosmological framework. We consider both the monopole and quadrupole multipole moments of the redshift-space two-point correlation function, as well as the radial and transverse clustering wedges, in the comoving scale range $10 30$ \Mpch, the discrepancy is reduced below $5\%$. At higher redshifts, we find instead an overall good agreement between measurements and model predictions. Though this accuracy is good enough for clustering analyses in current redshift surveys, the models have to be further improved not to introduce significant systematics in RSD constraints from next generation galaxy surveys. The effect of redshift errors is degenerate with the one of small-scale random motions, and can be marginalised over in the statistical analysis, not introducing any statistically significant bias in the linear growth constraints, especially at $z\geq1$.

astro-ph.CO↗

arXiv2018

Effect of observational holes in fractal analysis of galaxy survey masks

Observations reveal that the Universe has a hierarchy of galaxy clustering with transition to homogeneity on large scales according to the $Λ$CDM model. On the other hand some observational estimates suggest a multifractal behavior where galactic clustering is based on generalization of the correlation dimension. We study the influence of veto areas on fractal measurements in masks of galaxy surveys. We investigate if these holes can produce fractal behaviors or modify the scale of cosmic homogeneity. From the footprint of BOSS-DR12, we build a homogeneous sample following the radial selection function for 73,412 points limited to the redshift range $0.002<z<0.2$. Different percentages of observational holes were created cumulatively in RA and dec on the sample. For the synthetic sample and for a real sample of galaxies we determined the fractal dimension $D_q(r)$ in the range $2\leq q\leq6$ using the sliding window technique to characterize the spatial point distribution. Our results show that generalized dimension varies with the scale, for low scales there are a fractal behavior with fluctuations for all hole percentages studied and for larger scales than 113 Mpc/h the statistical homogeneity is achieved in concordance with other analysis. We find that observational holes cause a shift in the homogeneity scale $r_H$, in particular for synthetic samples with percentages of holes between 0-10% the homogeneity scale is reached at $(83\pm1)$Mpc/h while the fractal dimension changes as $2.83^{\pm0.09}\leq D_q\leq2.855^{\pm0.09}$. For synthetic samples with percentages of holes greater than 10%, we find that the value of $r_H$ increases proportionally. Consequently future results about homogeneity scale based in fractal analyses must be corrected by observational holes and regions of incompleteness in the geometry of the galaxy catalogue if the size of the veto mask is significant.

astro-ph.CO↗

arXiv2012

Multifractal analysis and lacunarity spectrum of the galaxies of the ninth Sloan Digital Sky Survey (SDSS) data release

In this work, we develop a statistical analysis of the large-scale clustering of matter in the Universe from the fractal point of view using galaxies from the Ninth Sloan Digital Sky Survey (SDSS) Data Release (DR9). From the total set of galaxies, a magnitude-limited sample of galaxies with redshifts in the range 0 < z < 0.15 was created. The sample covers the largest completely connected area of the celestial sphere within the catalogue, with limits in right ascension from 120 to 240 degrees and declination from 0 to 60 degrees, which is a region that includes the largest galactic samples that have been studied from the fractal viewpoint to date. The sample contains 164,168 galaxies. Using the sliding-window technique, the multifractal dimension spectrum and its dependence on radial distance are determined. This generalisation of the concept of fractal dimension is used to analyse large-scale clustering of matter in complex systems. Likewise, the lacunarity spectrum, which is a quantity that complements the characterisation of a fractal set by quantifying how the set fills the space in which it is embedded, is determined. Using these statistical tools, we find that the clustering of galaxies exhibits fractal behaviour that depends on the radial distance for all calculated quantities. A transition to homogeneity is not observed in the calculation of the fractal dimension of galaxies; instead, the galaxies exhibit a multifractal behaviour whose dimensional spectrum does not exceed the physical spatial dimension for radial distances up to 180 Mpc/h from each centre within the sample. Our results and their implications are discussed in the context of the formation of large-scale structures in the Universe.

astro-ph.CO↗

arXiv2012

Millennium Simulation Dark Matter Haloes: Multi-fractal and Lacunarity Analysis with Homogeneity Transition

We investigate from the fractal viewpoint the way in which the dark matter is grouped at z = 0 in the Millennium dark matter cosmological simulation. The determination of the cross to homogeneity in the Millennium Simulation data is described from the behaviour of the fractal dimension and the lacunarity. We use the sliding window technique to calculate the fractal mass-radius dimension, the pre-factor F and the lacunarity of this fractal relation. Besides, we determinate the multi-fractal dimension and the lacunarity spectrum, including their dependence with radial distance. This calculations show a radial distance dependency of all the fractal quantities, with heterogeneity clustering of dark matter haloes up to depths of 100 Mpc/h. The dark matter haloes clustering in the Millennium Simulation shows a radial distance dependency, with two regions clearly defined. The lacunarity spectrum for values of the structure parameter q >= 1 shows regions with relative maxima, revealing the formation of clusters and voids in the dark matter haloes distribution. With the use of the multi-fractal dimension and the lacunarity spectrum, the transition to homogeneity at depths between 100 Mpc/h and 120 Mpc/h for the Millennium Simulation dark matter haloes is detected.

astro-ph.CO↗