arXiv subjects

Camila P. Novaes

Publications and source records attributed to Camila P. Novaes.

23 records · Page 2Linked to original sources

arXiv2021

Baryon Acoustic Oscillations from Integrated Neutral Gas Observations: an instrument to observe the 21cm hydrogen line in the redshift range 0.13 $<$ z $<$ 0.45 -- status update

BINGO (BAO from Integrated Neutral Gas Observations) is a unique radio telescope designed to map the intensity of neutral hydrogen distribution at cosmological distances, making the first detection of Baryon Acoustic Oscillations (BAO) in the frequency band 980 MHz - 1260 MHz, corresponding to a redshift range $0.127 < z < 0.449$. BAO is one of the most powerful probes of cosmological parameters and BINGO was designed to detect the BAO signal to a level that makes it possible to put new constraints on the equation of state of dark energy. The telescope will be built in Paraíba, Brazil and consists of two $\thicksim$ 40m mirrors, a feedhorn array of 28 horns, and no moving parts, working as a drift-scan instrument. It will cover a $15^{\circ}$ declination strip centered at $\sim δ=-15^{\circ}$, mapping $\sim 5400$ square degrees in the sky. The BINGO consortium is led by University of São Paulo with co-leadership at National Institute for Space Research and Campina Grande Federal University (Brazil). Telescope subsystems have already been fabricated and tested, and the dish and structure fabrication are expected to start in late 2020, as well as the road and terrain preparation.

astro-ph.CO↗

arXiv2018

Constraining neutrino mass with weak lensing Minkowski Functionals

The presence of massive neutrinos affects structure formation, leaving imprints on large-scale structure observables such as the weak lensing field. The common lensing analyses with two-point statistics are insensitive to the large amount of non-Gaussian information in the density field. We investigate non-Gaussian tools, in particular the Minkowski Functionals (MFs)---morphological descriptors including area, perimeter, and genus---in an attempt to recover the higher-order information. We use convergence maps from the Cosmological Massive Neutrino Simulations (\texttt{MassiveNus}) and assume galaxy noise, density, and redshift distribution for an LSST-like survey. We show that MFs are sensitive to the neutrino mass sum, and the sensitivity is redshift dependent and is non-Gaussian. We find that redshift tomography significantly improves the constraints on neutrino mass for MFs, compared to the improvements for the power spectrum. We attribute this to the stronger redshift dependence of neutrino effects on small scales. We then build an emulator to model the power spectrum and MFs, and study the constraints on $[M_ν$, $Ω_{m}$, $A_{s}]$ from the power spectrum, MFs, and their combination. We show that MFs significantly outperform the power spectrum in constraining neutrino mass, by more than a factor of four. However, a thorough study of the impact from systematics such as baryon physics and galaxy shape and redshift biases will be important to realize the full potential of MFs.

astro-ph.CO↗

arXiv2018

Topology and the suppression of CMB large-angle correlations

To date, no compelling evidence has been found that the universe has non-trivial spatial topology. Meanwhile, anomalies in the observed CMB temperature map, such as the lack of correlations at large angular separations, remain observationally robust. We show that if our universe is flat and has one compact dimension of appropriate size (slab topology), this would suppress large-angle temperature correlations while maintaining a low-$\ell$ angular power spectrum consistent with observations. The optimal length appears to be $1.4$ times the conformal radius of the CMB's last scattering surface ($χ_{rec}$). We construct the probability distribution function of the statistic $S_{1/2}$ using simulated Sachs-Wolf-only skies for each of several values of $L_z/χ_{rec}$. For $L_z\simeq1.4χ_{rec}$ the $p$-value of four standard masked Planck maps is $p\simeq0.15$, compared to $p\lesssim0.003$ for the conventional topologically trivial space. The mean angular power spectrum $\langle C_{\ell} \rangle$ of the $L_z=1.4χ_{rec}$ slab space matches the observed power spectrum at $2\leq\ell\lesssim6$ -- including a substantially suppressed quadrupole $C_2$, a slightly suppressed octopole $C_3$, and unsuppressed higher multipoles. It does not predict other low-$\ell$ CMB anomalies, and does not take account of normally sub-dominant Integrated Sachs Wolfe contributions. An $L_z=1.4χ_{rec}$ slab topology is consistent with published limits from the Planck maps ($L_z\gtrsim1.12χ_{rec}$). It is within the 95% confidence range $1.2\leq L_z/χ_{rec}\leq2.1$ inferred using the covariance-matrix of temperature fluctuations. However, it violates published circles-in-the-sky limits from WMAP and related unpublished limits from Planck ($L_z/χ_{rec}\gtrsim1.9$). We remark on the possibility to satisfy these limits, and "postdict" other large-angle anomalies, with closely related topologies.

astro-ph.CO↗

arXiv2018

Tomographic local 2D analyses of the WISExSuperCOSMOS all-sky galaxy catalogue

The recent progress in obtaining larger and deeper galaxy catalogues is of fundamental importance for cosmological studies, especially to robustly measure the large scale density fluctuations in the Universe. The present work uses the Minkowski Functionals (MF) to probe the galaxy density field from the WISExSuperCOSMOS (WSC) all-sky catalogue by performing tomographic local analyses in five redshift shells (of thickness $δz = 0.05$) in the total range of $0.10 < z < 0.35$. Here, for the first time, the MF are applied to 2D projections of the galaxy number count (GNC) fields with the purpose of looking for regions in the WSC catalogue with unexpected features compared to $Λ$CDM mock realisations. Our methodology reveals 1 - 3 regions of the GNC maps in each redshift shell with an uncommon behaviour (extreme regions), i.e., $p$-value $<$ 1.4\%. Indeed, the resulting MF curves show signatures that suggest the uncommon behaviour to be associated with the presence of over- or under-densities there, but contamination due to residual foregrounds is not discarded. Additionally, even though our analyses indicate a good agreement among data and simulations, we identify 1 highly extreme region, seemingly associated to a large clustered distribution of galaxies. Our results confirm the usefulness of the MF to analyse GNC maps from photometric galaxy datasets.

astro-ph.CO↗

arXiv2015

Primordial Non-Gaussianities of inflationary step-like models

We use Minkowski Functionals to explore the presence of non-Gaussian signatures in simulated cosmic microwave background (CMB) maps. Precisely, we analyse the non-Gaussianities produced from the angular power spectra emerging from a class of inflationary models with a primordial step-like potential. This class of models are able to perform the best-fit of the low-$\ell$ `features', revealed first in the CMB angular power spectrum by the WMAP experiment and then confirmed by the Planck collaboration maps. Indeed, such models generate oscillatory features in the primordial power spectrum of scalar perturbations, that are then imprinted in the large scales of the CMB field. Interestingly, we discover Gaussian deviations in the CMB maps simulated from the power spectra produced by these models, as compared with Gaussian $Λ$CDM maps. Moreover, we also show that the kind and level of the non-Gaussianities produced in these simulated CMB maps are compatible with that found in the four foreground-cleaned Planck maps. Our results indicate that inflationary models with a step-like potential are not only able to improve the best-fit respect to the $Λ$CDM model accounting well for the `features' observed in the CMB angular power spectrum, but also suggesting a possible origin for certain non-Gaussian signatures observed in the Planck data.

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