Dark Energy Survey year 1 results: Constraints on extended cosmological models from galaxy clustering and weak lensing

摘要

We present constraints on extensions of the minimal cosmological models dominated by dark matter and dark energy, ΛCDM and wCDM, by using a combined analysis of galaxy clustering and weak gravitational lensing from the first-year data of the Dark Energy Survey (DES Y1) in combination with external data.We consider four extensions of the minimal dark energy-dominated scenarios: (1) nonzero curvature Ω_k,(2) number of relativistic species N_(eff) different from the standard value of 3.046, (3) time-varying equationof- state of dark energy described by the parameters w_0 and w_a (alternatively quoted by the values at the pivot redshift, w_p, and w_a), and (4) modified gravity described by the parameters μ_0 and Σ_0 that modify the metric potentials. We also consider external information from Planck cosmic microwave background measurements; baryon acoustic oscillation measurements from SDSS, 6dF, and BOSS; redshift-space distortion measurements from BOSS; and type Ia supernova information from the Pantheon compilation of datasets. Constraints on curvature and the number of relativistic species are dominated by the external data; when these are combined with DES Y1, we find Ω_k = 0.0020_(-0.0032)~(+0.0037) at the 68% confidence level, and the upper limit N_(eff) < 3.28(3.55) at 68% (95%) confidence, assuming a hard prior N_(eff) > 3.0. For the timevarying equation-of-state, we find the pivot value (w_p, w_a) = (-0.91_(-0.23)~(+0.19);-0.57_(-1.11)~(+0.93) ) at pivot redshift z_p = 0.27 from DES alone, and (w_p, w_a) = (-1.01_(-0.04)~(+0.04) ;-0.28_(-0.48)~(+0.37) ) at z_p = 0.20 from DES Y1 combined with external data; in either case we find no evidence for the temporal variation of the equation of state. For modified gravity, we find the present-day value of the relevant parameters to be Σ_0 = 0.43_(-0.29)~(+0.28) from DES Y1 alone, and (Σ_0, μ_0) = (0.06_(-0.07)~(+0.08);-0.11_(-0.46)~(+0.42)) from DES Y1 combined with external data. These modified-gravity constr