6 research outputs found
Developing a unified pipeline for large-scale structure data analysis with angular power spectra -- I. The importance of redshift-space distortions for galaxy number counts
We develop a cosmological parameter estimation code for (tomographic) angular
power spectra analyses of galaxy number counts, for which we include, for the
first time, redshift-space distortions (RSD) in the Limber approximation. This
allows for a speed-up in computation time, and we emphasise that only angular
scales where the Limber approximation is valid are included in our analysis.
Our main result shows that a correct modelling of RSD is crucial not to bias
cosmological parameter estimation. This happens not only for
spectroscopy-detected galaxies, but even in the case of galaxy surveys with
photometric redshift estimates. Moreover, a correct implementation of RSD is
especially valuable in alleviating the degeneracy between the amplitude of the
underlying matter power spectrum and the galaxy bias. We argue that our
findings are particularly relevant for present and planned observational
campaigns, such as the Euclid satellite or the Square Kilometre Array, which
aim at studying the cosmic large-scale structure and trace its growth over a
wide range of redshifts and scales.Comment: 18 pages, 11 figures, 4 tables. New expression for RSDs in Limber
approximation (Eq. 9), much easier to implement in numerical codes. Results
on "conservative scenario" slightly change
Model-independent constraints on clustering and growth of cosmic structures from BOSS DR12 galaxies in harmonic space
We present a new, model-independent measurement of the clustering amplitude
of galaxies and the growth of cosmic large-scale structures from the Baryon
Oscillation Spectroscopic Survey (BOSS) 12th data release (DR12). This is
achieved by generalising harmonic-space power spectra for galaxy clustering to
measure separately the magnitudes of the density and of the redshift-space
distortion terms, which are respectively related to the clustering amplitude,
, and the growth, . We adopt a tomographic approach
with 15 redshift bins in the range . We restrict our analysis
to strictly linear scales, implementing a redshift-dependent maximum multipole
for each of the tomographic bins. Thus, we obtain 30 data points in total, 15
for each of the quantities and . The measurements
do not appear to suffer from any apparent systematic effect and show excellent
agreement with the theoretical prediction from a concordance cosmology as from
the Planck satellite. Our results also agree with previous analyses by the BOSS
collaboration. Although each single datum has, in general, a larger error bar
than that obtained in configuration- or Fourier-space analyses, our study
provides the community with a larger number of tomographic data points that
allow for a complementary tracking in redshift of the evolution of fundamental
cosmological quantities.Comment: 14 pages, 8 figures, 3 tables. To be submitted soo
Developing a unified pipeline for large-scale structure data analysis with angular power spectra -- III. Implementing the multi-tracer technique to constrain neutrino masses
In this paper, we apply the multi-tracer technique to harmonic-space (i.e.\
angular) power spectra with a likelihood-based approach. This goes beyond the
usual Fisher matrix formalism hitherto implemented in forecasts with angular
statistics, opening up a window for future developments and direct application
to available data sets. We also release a fully-operational modified version of
the publicly available code CosmoSIS, where we consistently include all the
add-ons presented in the previous papers of this series. The result is a
modular cosmological parameter estimation suite for angular power spectra of
galaxy number counts, allowing for single and multiple tracers, and including
density fluctuations, redshift-space distortions, and weak lensing
magnification. We demonstrate the improvement on parameter constraints enabled
by the use of multiple tracers on a multi-tracing analysis of luminous red
galaxies and emission line galaxies. We obtain an enhancement of on the
upper bound on the sum of neutrino masses. Our code is publicly
available at
https://github.com/ktanidis/Modified_CosmoSIS_for_galaxy_number_count_angular_power_spectra.Comment: 10 pages, 5 figures, 4 tables. Corrected minor typos; added Fig. 1;
version matching submission to MNRAS journal. Comments are welcom
Honing cross-correlation tools for inference on ultra-high-energy cosmic-ray composition
The chemical composition of the highest-energy cosmic rays, namely the atomic
number of rays with energies , remains to date largely
unknown. Some information on the composition can be inferred from the
deflections that charged ultra-high-energy cosmic rays experience while they
traverse intervening magnetic fields. Indeed, such deflections distort and
suppress the original anisotropy in the cosmic rays arrival directions; thus, a
measure of the anisotropy is also a measurement of the deflections, which in
turn informs us on the chemical composition. In this work, we show that, by
quantifying ultra-high-energy cosmic ray anisotropies through the angular,
harmonic cross-correlation between cosmic rays and galaxies, we are able to
exclude iron fractions on a fiducial hydrogen
map at level, and even smaller fractions in the reverse case of
hydrogen on an iron map, going below when we mask the
Galactic Centre up to latitudes of . This is an improvement of
a factor of a few compared to our previous method, and is mostly ascribable to
a new test statistics which is sensitive to each harmonic multipole
individually. Our method can be applied to real data as an independent test of
the recent claim that current cosmic-ray data can not be reproduced by any
existing model of the Galactic magnetic field, as well as an additional handle
to compare any realistic, competing, data-driven composition models.Comment: 9 pages, 3 figures + appendix. To be submitte
Developing a unified pipeline for large-scale structure data analysis with angular power spectra – II. A case study for magnification bias and radio continuum surveys
Following on our purpose of developing a unified pipeline for large-scale structure data analysis with angular power spectra, we now include the weak lensing effect of magnification bias on galaxy clustering in a publicly available, modular parameter estimation code. We thus forecast constraints on the parameters of the concordance cosmological model, dark energy, and modified gravity theories from galaxy clustering tomographic angular power spectra. We find that a correct modelling of magnification is crucial not to bias the parameter estimation, especially in the case of deep galaxy surveys. Our case study adopts specifications of the Evolutionary Map of the Universe, which is a full-sky, deep radio-continuum survey, expected to probe the Universe up to redshift z ∼ 6. We assume the Limber approximation, and include magnification bias on top of density fluctuations and redshift-space distortions. By restricting our analysis to the regime where the Limber approximation holds true, we significantly minimize the computational time needed, compared to that of the exact calculation