The LSST-DESC 3x2pt Tomography Optimization Challenge
The Open Journal of Astrophysics The Open Journal 4:1 (2021)
The growth of density perturbations in the last ∼10 billion years from tomographic large-scale structure data
Journal of Cosmology and Astroparticle Physics IOP Publishing 10:2021 (2021) 030
Abstract:
In order to investigate the origin of the ongoing tension between the amplitude of matter fluctuations measured by weak lensing experiments at low redshifts and the value inferred from the cosmic microwave background anisotropies, we reconstruct the evolution of this amplitude from z ∼ 2 using existing large-scale structure data. To do so, we decouple the linear growth of density inhomogeneities from the background expansion, and constrain its redshift dependence making use of a combination of 6 different data sets, including cosmic shear, galaxy clustering and CMB lensing. We analyze these data under a consistent harmonic-space angular power spectrum-based pipeline. We show that current data constrain the amplitude of fluctuations mostly in the range 0.2 < z < 0.7, where it is lower than predicted by Planck. This difference is mostly driven by current cosmic shear data, although the growth histories reconstructed from different data combinations are consistent with each other, and we find no evidence of systematic deviations in any particular experiment. In spite of the tension with Planck, the data are well-described by the ΛCDM model, albeit with a lower value of S8 ≡ σ8(Ωm/0.3)0.5 . As part of our analysis, we find constraints on this parameter of S8 = 0.7781 ± 0.0094 (68% confidence level), reaching almost percent-level errors comparable with CMB measurements, and 3.4σ away from the value found by Planck.Hefty enhancement of cosmological constraints from the DES Y1 data using a hybrid effective field theory approach to galaxy bias
Journal of Cosmology and Astroparticle Physics IOP Publishing 2021:09 (2021) 020-020
Linear anisotropies in dispersion-measure-based cosmological observables
Physical Review D - Particles, Fields, Gravitation and Cosmology American Physical Society 103 (2021) 123544
Abstract:
We derive all contributions to the dispersion measure (DM) of electromagnetic pulses to linear order in cosmological perturbations, including both density fluctuations and relativistic effects. We then use this result to calculate the power spectrum of DM-based cosmological observables to linear order in perturbations. In particular we study two cases: maps of the dispersion measure from a set of localized sources (including the effects of source clustering), and fluctuations in the density of DM-selected sources. The impact of most relativistic effects is limited to large angular scales, and is negligible for all practical applications in the context of ongoing and envisaged observational programmes targetting fast radio bursts. We compare the leading contributions to DM-space clustering, including the effects of gravitational lensing, and find that the signal is dominated by the fluctuations in the free electron column density, rather than the local source clustering or lensing contributions. To compensate for the disappointing irrelevance of relativistic effects, we re-derive them in terms of the geodesic equation for massive particles in a perturbed Friedmann-Robertson-Walker metric.Microwave spectro-polarimetry of matter and radiation across space and time
Experimental Astronomy Springer Nature 51:3 (2021) 1471-1514