Abstract
Velocity fields provide a complementary avenue to constrain cosmological information, either through the peculiar velocity surveys or the kinetic Sunyaev Zel’dovich effect. One of the commonly used statistics is the mean radial pairwise velocity. Here, we consider the three-point mean relative velocity (i.e. the mean relative velocities between pairs in a triplet). Using halo catalogs from the Quijote suite ofN-body simulations, we first showcase how the analytical prediction for the mean relative velocities between pairs in a triplet achieve better than 4−5% accuracy using standard perturbation theory at leading order for triangular configurations with a minimum separation ofr ≥ 50 h−1Mpc. Furthermore, we present the mean relative velocity between pairs in a triplet as a novel probe of neutrino mass estimation. We explored the full cosmological information content of the halo mean pairwise velocities and the mean relative velocities between halo pairs in a triplet. We did this through the Fisher-matrix formalism using 22 000 simulations from the Quijote suite and by considering all triangular configurations with a minimum and a maximum separation of 20 h−1Mpc and 120 h−1Mpc, respectively. We find that the mean relative velocities in a triplet allows a 1σneutrino mass (Mν) constraint of 0.065 eV, which is roughly 13 times better than the mean pairwise velocity constraint (0.877 eV). This information gain is not limited to neutrino mass, but it extends to other cosmological parameters: Ωm, Ωb,h,ns, andσ8, achieving an information gain of 8.9, 11.8, 15.5, 20.9, and 10.9 times, respectively. These results illustrate the possibility of exploiting the mean three-point relative velocities to constrain the cosmological parameters accurately from future cosmic microwave background experiments and peculiar velocity surveys.
Highlights
The last decades have witnessed a tremendous increase in our understanding of the underlying cosmological model
We restricted the plotting to these triangular configurations for two reasons: (i) we expected the analytical prediction to work well at these quasi-linear scales and above, and (ii) we reduced the number of total triangular configurations considered in the plot to highlight the configurations that are most interesting for comparison purposes
If we focus on the triangular configuration ‘165’, we find that both Rh12 and Rh23 over-predict the measurement by 4.6%, and this configuration corresponds to the equilateral triangle with a separation length between 90 and 95 h−1 Mpc
Summary
The last decades have witnessed a tremendous increase in our understanding of the underlying cosmological model. This has been mainly facilitated by cosmic microwave background (CMB) experiments (e.g. Planck Collaboration VI 2020), galaxy redshift surveys (e.g. eBOSS Collaboration 2021), and gravitational lensing surveys As the complex galaxy distribution represents a non-Gaussian field, higher order statistics such as the bispectrum and the three-point correlation function contain additional information. By considering both two-point and three-point clustering information, future redshift surveys will be able to obtain a substantial improvement with regard to the cosmological parameter constraints This will be possible as the free-streaming of neutrinos imprint unique signatures on galaxy clustering information in both real and redshift space (e.g. Saito et al 2008; Wong 2008; Castorina et al 2015; Villaescusa-Navarro et al 2018; García-Farieta et al 2019; Kamalinejad & Slepian 2020)
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