arXiv subjects

Pedro da Silveira Ferreira

Publications and source records attributed to Pedro da Silveira Ferreira.

8 recordsLinked to original sources

arXiv2026

Angular BAO Measurements with the DESI DR1 BGS Sample

We employ a model-independent approach in both the correlation function estimation and the angular BAO feature estimation by computing the angular two-point correlation function. First, we conducted a series of tests to the available DESI tracers to check their representativeness to angular clustering; the result was that, considering the completeness of the first data release across the footprint, we could only make use of the BGS sample for the effective redshifts 0.21 (BGS1) and 0.25 (BGS2). For a reliable analysis in such low redshift, we use the bootstrap of the data itself to construct a covariance matrix that accounts for systematics. We use a purely statistical method to correct the projection effects and find that our results show reasonable agreement with the $θ_{\rm BAO}$ expected by the CPL parameters obtained by DESI DR1, being BGS1 $12.77 \pm 1.15$ degrees and BGS2 $11.70 \pm 1.21$ degrees. This means a tension at the $2.4σ$ ($2.7σ$) level for BGS1 (BGS2) CPL parametrization, while a $2.84σ$ ($3.02σ$) discrepancy within the predicted by $Λ$CDM. We conclude that, with the current sample available, the use of an angular correlation function serving as the BAO probe, although prefers the CPL parametrization, does not provide conclusive results regarding the best cosmological model.

astro-ph.CO↗

arXiv2026

Filament-Arm Node Systems (FANS): A new probe of the winding and chirality of the cosmic web

We define Filament-Arm Node Systems (FANS), a new class of cosmic-web objects consisting of multiple filament arms connected to a common node, and use their geometry to construct an object-based test of cosmic chirality. With the cosmic-web node providing a natural reference point, FANS span characteristic scales of ~60Mpc/h, allowing the coherent winding of their arms around the node to be measured directly. We define cosmic spirality as the amplitude of this winding and handedness as its signed clockwise (CW) or counter-clockwise (CCW) sense. We further introduce an axis-conditioned extrinsic estimator that searches for the projected signature of a coherent three-dimensional axial pattern of the handedness field, corresponding to a preferred axis of winding. Applying these measurements to two distinct SDSS filament reconstructions, and assessing their significance with sign-flip nulls and 27 controlled variations of the FANS construction parameters, we find no significant preference for CW or CCW winding, either globally or around a preferred axis. The data are therefore consistent with parity symmetry, as expected in standard LCDM cosmology. We additionally find that cosmic spirality decreases with cosmic time, a trend that may reflect the gravitational straightening of filament arms. These first constraints establish FANS as a new probe of cosmic-web symmetry and large-scale morphology and provide a baseline for future parity tests with the much larger filament samples expected from upcoming surveys.

astro-ph.CO↗

arXiv2026

Where Galaxies Point: First Measurement of the Large-Scale Axial Intrinsic Alignment

We report evidence for large-scale axial intrinsic alignment (LAIA): a coherent axis shared by galaxies and cosmic-web filaments. Applying an orientation-field estimator to Dark Energy Survey (DES) Y3 shape data, we identify a preferred axis in galaxy orientations. Ellipticals' semi-major and spirals' semi-minor axes align with it, producing a $4.7σ$ signal whose pattern and amplitude hierarchy are consistent with morphology-dependent tidal-alignment and tidal-torquing expectations. Independently, Sloan Digital Sky Survey (SDSS) filament catalogues yield a compatible axis: northern and southern Galactic samples agree within $\simeq1σ$, the combined signal reaches $12.6σ$, and the axis lies within $\simeq2σ$ of the high-redshift galaxy sample direction. Because DES and SDSS footprints overlap marginally, this agreement is unlikely to arise from direct galaxy--filament alignment. It therefore provides a multi-survey, multi-observable test of a large-scale orientation field, stable under redshift and systematics tests. $N$-body mocks based on an isotropic $Λ$CDM cosmology with standard intrinsic-alignment prescriptions, including Euclid Flagship 2 and MICECAT v2, do not reproduce the pattern. LAIA provides a new statistical-isotropy probe linking galaxy morphology, cosmic-web structure and large-scale tidal fields.

astro-ph.CO↗

arXiv2026

The CMB Cold Spot under the lens II: Lensing signatures in polarization and cosmic texture footprints

We forecast the detectability of the lensing footprint of a collapsing cosmic texture, a topological defect proposed as an explanation of the CMB Cold Spot. Our pipeline is a quadratic, template-amplitude estimator for localized, azimuthally symmetric lensing profiles: it projects the standard off-diagonal covariance response of lensed CMB fields onto a physically motivated template. Rather than reconstructing an arbitrary lensing field, the method targets weak but coherent localized footprints from sources such as voids, clusters and topological defects. Using the temperature/polarization pairs TT, TE+ET, EE, TB+BT and EB+BE for forthcoming Simons Observatory data, we estimate a $2.3σ$ detection if the texture amplitude reaches the current Planck 2018 $2σ$ upper limit, and a $1.5σ$ measurement for the best-fit texture parameters. This sensitivity is notable given the expected typical deflection angle below $6''$. The inclusion of polarization substantially increases the cumulative signal-to-noise ratio, by $\sim67\%$ relative to temperature alone, making sub-$10''$ localized lensing footprints accessible to SO-like surveys.

astro-ph.CO↗

arXiv2024

Tomographic redshift dipole: Testing the cosmological principle

The cosmological principle posits that the universe is statistically homogeneous and isotropic on large scales, implying all matter shares the same rest frame. This principle suggests that velocity estimates of our motion from various sources should agree with the cosmic microwave background (CMB) dipole's inferred velocity of 370 km/s. Yet, for over two decades, analyses of radio galaxy and quasar catalogs have found velocities at odds with the CMB dipole, with tensions up to 5$σ$. In a blind analysis of BOSS and eBOSS spectroscopic data from galaxies and quasars across $0.2<z<2.2$, we applied a novel dipole estimator for a tomographic approach, robustly correcting biases and quantifying uncertainties with realistic mock catalogs. Our findings with eBOSS data ($0.6<z<2.2$), indicating a velocity of $196^{+92}_{-79}$ km/s, demonstrate a $2σ$ agreement with the CMB dipole when considering the full 3D vector distribution and a 3-to-6$σ$ tension with previous number count studies. This result supports the cosmological principle, emphasizing the consistency of our motion with the CMB across vast cosmic distances. On the other hand, the BOSS data revealed potential unmodeled systematics; the estimator could not be minimized using the LOWZ set ($0.2<z<0.4$), and the CMASS set ($0.4<z<0.6$) presented results that pointed towards the southern hemisphere, conflicting with the CMB dipole. Addressing the disparities with earlier number count analyses and understanding possible systematics in spectroscopic measurements will be essential to further validate the cosmological principle.

astro-ph.CO↗

arXiv2023

The CMB cold spot under the lens: ruling out a supervoid interpretation

The Cosmic Microwave Background (CMB) anisotropies are thought to be statistically isotropic and Gaussian. However, several anomalies are observed, including the CMB Cold Spot, an unexpected cold $\sim 10^{\circ}$ region with $p$-value $\lesssim 0.01$ in standard $Λ$CDM. One of the proposed origins of the Cold Spot is an unusually large void on the line of sight, that would generate a cold region through the combination of integrated Sachs-Wolfe and Rees-Sciama effects. In the past decade extensive searches were conducted in large scale structure surveys, both in optical and infrared, in the same area for $z \lesssim 1$ and did find evidence of large voids, but of depth and size able to account for only a fraction of the anomaly. Here we analyze the lensing signal in the Planck CMB data and rule out the hypothesis that the Cold Spot could be due to a large void located anywhere between us and the surface of last scattering. In particular, computing the evidence ratio we find that a model with a large void is disfavored compared to $Λ$CDM, with odds 1 : 13 (1 : 20) for SMICA (NILC) maps, compared to the original odds 56 : 1 (21 : 1) using temperature data alone.

astro-ph.CO↗

arXiv2021

First constraints on the intrinsic CMB dipole and our velocity with Doppler and aberration

We test the usual hypothesis that the Cosmic Microwave Background (CMB) dipole, its largest anisotropy, is due to our peculiar velocity with respect to the Hubble flow by measuring independently the Doppler and aberration effects on the CMB using Planck 2018 data. We remove the spurious contributions from the conversion of intensity into temperature and arrive at measurements which are independent from the CMB dipole itself for both temperature and polarization maps and both SMICA and NILC component-separation methods. Combining these new measurements with the dipole one we get the first constraints on the intrinsic CMB dipole. Assuming a standard dipolar lensing contribution we can put an upper limit on the intrinsic amplitude: 3.7 mK (95% CI). We estimate the peculiar velocity of the solar system without assuming a negligible intrinsic dipole contribution: $v = (300^{+111}_{-93})$ km/s with $(l,b) = (276 \pm 33, 51 \pm 19)^\circ$ [SMICA], and $v = (296^{+111}_{-88})$ km/s with $(l,b) = (280 \pm 33, 50 \pm 20)^\circ$ [NILC] with negligible systematic contributions. These values are consistent with the peculiar velocity hypothesis of the dipole.

astro-ph.CO↗

arXiv2021

Disentangling Doppler modulation, aberration and the temperature dipole in the CMB

An observer in relative motion to the Cosmic Microwave Background (CMB) rest frame is sensitive to both aberration and Doppler effects. Both effects introduce similar but non-identical off-diagonal couplings in the spherical harmonic coefficients. The CMB temperature dipole may have additional contributions from an intrinsic component, which in turn produces different aberration and Doppler couplings. Moreover, the standard conversion from intensity measurements into temperature also introduces spurious Doppler-like couplings. In order to learn about the intrinsic dipole it is therefore important to measure both aberration and Doppler couplings in an independent manner while also removing the spurious contributions from unit conversion, which are degenerate with the dipole. Here we present a pipeline to measure the Doppler and aberration signal independently from each other and from the dipole itself. We also consider realistic beaming, noise and mask effects. Our pipeline results in independent and unbiased estimators which have uncertainties only ~20% larger than the simple theoretical expectations. We discuss the achievable precision in each measurement for Planck 2018, and also forecast them for future ground-based experiments with the Simons Observatory and CMB-S4. An alternative pipeline is presented in order to cross-check results and improve robustness.

astro-ph.CO↗