Dark Energy Survey Year 1 Results: Constraints on Extended Cosmological Models from Galaxy Clustering and Weak Lensing

Abstract

We present constraints on extensions of the minimal cosmological models dominated by dark matter and dark energy, $\Lambda$CDM and $w$CDM, 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 ${\Omega }_k$, 2) number of relativistic species $N_{\mathrm{eff}}$ different from the standard value of 3.046, 3) time-varying equation-of-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 ${\mu }_0$ and ${\Sigma }_0$ that modify the metric potentials. We also consider external information from Planck CMB measurements; BAO measurements from SDSS, 6dF, and BOSS; RSD measurements from BOSS; and SNIa information from the Pantheon compilation. Constraints on curvature and the number of relativistic species are dominated by the external data; when these are combined with DES Y1, we find ${\Omega }_k=0.0020_{-0.0032}^{+0.0037}$ at the 68% confidence level, and $N_{\mathrm{eff}}<3.28(3.55)$ at 68% (95%) confidence. For the time-varying 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 ${\Sigma }_0=0.43_{-0.29}^{+0.28}$ from DES Y1 alone, and $({\Sigma }_0,{\mu }_0)=(0.06_{-0.07}^{+0.08},-0.11_{-0.46}^{+0.42})$ from DES Y1 combined with external data, consistent with predictions from GR.

Comments: 22 pages, 7 figures, matches the published version