Density split statistics: Cosmological constraints from counts and lensing in cells in DES Y1 and SDSS data
Abstract
We derive cosmological constraints from the probability distribution function (PDF) of evolved largescale matter density fluctuations. We do this by splitting lines of sight by density based on their count of tracer galaxies, and by measuring both gravitational shear around and countsincells in overdense and underdense lines of sight, in Dark Energy Survey (DES) First Year and Sloan Digital Sky Survey (SDSS) data. Our analysis uses a perturbation theory model [O. Friedrich et al., Phys. Rev. D 98, 023508 (2018), 10.1103/PhysRevD.98.023508] and is validated using N body simulation realizations and lognormal mocks. It allows us to constrain cosmology, bias and stochasticity of galaxies with respect to matter density and, in addition, the skewness of the matter density field. From a Bayesian model comparison, we find that the data weakly prefer a connection of galaxies and matter that is stochastic beyond Poisson fluctuations on ≤20 arcmin angular smoothing scale. The two stochasticity models we fit yield DES constraints on the matter density Ω_{m}=0.2 6_{0.03}^{+0.04} and Ω_{m}=0.2 8_{0.04}^{+0.05} that are consistent with each other. These values also agree with the DES analysis of galaxy and shear twopoint functions (3x2pt, DES Collaboration et al.) that only uses second moments of the PDF. Constraints on σ_{8} are model dependent (σ_{8}=0.9 7_{0.06}^{+0.07} and 0.8 0_{0.07}^{+0.06} for the two stochasticity models), but consistent with each other and with the 3 x 2pt results if stochasticity is at the low end of the posterior range. As an additional test of gravity, counts and lensing in cells allow to compare the skewness S_{3} of the matter density PDF to its Λ CDM prediction. We find no evidence of excess skewness in any model or data set, with better than 25 per cent relative precision in the skewness estimate from DES alone.
 Publication:

Physical Review D
 Pub Date:
 July 2018
 DOI:
 10.1103/PhysRevD.98.023507
 arXiv:
 arXiv:1710.05045
 Bibcode:
 2018PhRvD..98b3507G
 Keywords:

 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 33 pages, 22 figures