Beecroft Institute for Particle Astrophysics and Cosmology

Abstract:

ABSTRACT The peculiar velocity field of the local Universe provides direct insights into its matter distribution and the underlying theory of gravity, and is essential in cosmological analyses for modelling deviations from the Hubble flow. Numerous methods have been developed to reconstruct the density and velocity fields at $z \lesssim 0.05$, typically constrained by redshift-space galaxy positions or by direct distance tracers such as the Tully–Fisher relation, the Fundamental Plane, or Type Ia supernovae. We introduce a validation framework to evaluate the accuracy of these reconstructions against catalogues of direct distance tracers. Our framework assesses the goodness-of-fit of each reconstruction using Bayesian evidence, residual redshift discrepancies, velocity scaling, and the need for external bulk flows. Applying this framework to a suite of reconstructions – including those derived from the Bayesian Origin Reconstruction from Galaxies (BORG) algorithm and from linear theory – we find that the non-linear BORG reconstruction consistently outperforms others. We highlight the utility of such a comparative approach for supernova or gravitational wave cosmological studies, where selecting an optimal peculiar velocity model is essential. Additionally, we present calibrated bulk flow curves predicted by the reconstructions and perform a density–velocity cross-correlation using a linear theory reconstruction to constrain the growth factor, yielding $S_8 = 0.793 \pm 0.035$. The result is in good agreement with both weak lensing and Planck, but is in strong disagreement with some peculiar velocity studies.

Abstract:

We measure the amplitude of matter fluctuations over a wide range of redshifts by combining CMB lensing observations from ACT DR6 and Planck PR4 with the overdensity of quasars from Quaia, a Gaia and unWISE quasar catalog. Our analysis includes the CMB lensing power spectrum from ACT DR6, the auto-correlation of two Quaia quasar samples centered at z ≃ 1.0 and z ≃ 2.1, and their cross-correlations with CMB lensing from both ACT DR6 and Planck PR4. By performing a series of contamination and systematic null tests, we find no evidence for contamination in the lensing maps, contrary to what was suggested in previous Quaia cross-correlation analyses using Planck PR4 CMB lensing data. From the joint analysis of the quasar auto- and cross-correlations with CMB lensing, and including BOSS BAO data to break the degeneracy between Ω m and σ 8, we obtain σ 8 = 0.802+0.045 -0.057, consistent with ΛCDM predictions from Planck primary CMB measurements. We also find consistent results using DESI BAO data. Combining the CMB lensing auto-spectrum with the cross-correlation measurement improves the constraint on σ 8 by 12% relative to the lensing auto-spectrum alone, yielding σ 8 = 0.804 ± 0.013. This dataset combination also enables a reconstruction of structure growth across redshifts. We infer a 12% constraint on the amplitude of matter fluctuations at z > 3, with a measurement at the median redshift of the signal of σ 8(z̃ = 5.1) = 0.146+0.021 -0.014, consistent with Planck at the 1.4σ level. These results provide one of the highest redshift constraints on the growth of structure to date.

Abstract:

We present the first cosmological constraints from a joint analysis of galaxy clustering and galaxy–galaxy lensing using extended SubHalo Abundance Matching (SHAMe). We analyse stellar mass-selected Galaxy And Mass Assembly galaxy clustering and Kilo-Degree Survey (KiDS-1000) galaxy–galaxy lensing and find constraints on , in agreement with Planck at 1.7, with the mass density fluctuation amplitude in 8 sphere at present and the density parameter in total matter. These results are in agreement with the cosmic microwave background results from Planck. We are able to constrain all five SHAMe parameters, which describe the galaxy–subhalo connection. We validate our methodology by first applying it to simulated catalogues, generated from the TNG300 simulation, which mimic the stellar mass selection of our real data. We show that we are able to recover the input cosmology for both our fiducial and all-scale analyses. Our all-scale analysis extends to scales of galaxy–galaxy lensing below , which we exclude in our fiducial analysis to avoid baryonic effects. When including all scales, we find a value of , which is 1.26 higher than our fiducial result (against naive expectations where baryonic feedback should lead to small-scale power suppression), and in agreement with Planck at 0.9. We also find a 21 per cent tighter constraint on and a 29 per cent tighter constraint on compared to our fiducial analysis. This work shows the power and potential of joint small-scale galaxy clustering and galaxy–galaxy lensing analyses using SHAMe.

Abstract:

We present two extensive sets of 3500+1000 simulations of dark matter haloes on the past light cone and two corresponding sets of simulated (mock) galaxy catalogues that represent the spectroscopic sample of Euclid . The simulations were produced with the latest version of the code Pinocchio and provide the largest public set of simulated skies. The mock galaxy catalogues were obtained by populating haloes with galaxies using an halo occupation distribution (HOD) model extracted from the Flagship galaxy catalogue provided by Euclid Collaboration. The Geppetto set of 3500 simulated skies was obtained by tiling a 1.2 h −1 Gpc box to cover a light cone whose sky footprint is a circle with a radius of 30° for an area of 2763 deg 2 and a minimum halo mass of 1.5 × 10 11 h −1 M ⊙ . The relatively small size of the box means that this set is unsuitable for measuring very large scales. The EuclidLargeBox set consists of 1000 simulations of 3.38 h −1 Gpc and has the same mass resolution and a footprint that covers half of the sky. It excludes the Milky Way zone of avoidance. From this, we produced a set of 1000 EuclidLargeMocks on the 30° radius footprint, whose comoving volume is fully contained in the simulation box. We validated the two sets of catalogues by analysing number densities, power spectra, and two-point correlation functions to show that the Flagship spectroscopic catalogue is consistent with being one of the realisations of the simulated sets. We noted small deviations, however, that are limited to the quadrupole at k > 0.2 h Mpc −1 . We infer the cosmological parameters from these catalogues and demonstrate that using one realisation of EuclidLargeMocks in place of the Flagship mock produces the same posteriors to within the expected shift given by the sample variance. These simulated skies will be used for the galaxy clustering analysis of the Euclid Data Release 1 (DR1), and an even larger set of simulations is planned for the next releases.