# 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 $$N_{\rm eff}$$ 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 $$\Omega_k=0.0020^{+0.0037}_{-0.0032}$$ at the 68\% confidence level, and $$N_{\rm eff}<3.28\, (3.55)$$ at 68\% (95\%) confidence. For the time-varying equation-of-state, we find the pivot value $$(w_p, w_a)=(-0.91^{+0.19}_{-0.23}, -0.57^{+0.93}_{-1.11})$$ at pivot redshift $$z_p=0.27$$ from DES alone, and $$(w_p, w_a)=(-1.01^{+0.04}_{-0.04}, -0.28^{+0.37}_{-0.48})$$ 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 $$\Sigma_0= 0.43^{+0.28}_{-0.29}$$ from DES Y1 alone, and $$(\Sigma_0, \mu_0)=(0.06^{+0.08}_{-0.07}, -0.11^{+0.42}_{-0.46})$$ from DES Y1 combined with external data, consistent with predictions from GR.

- Authors:

- Publication Date:

- Research Org.:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States); Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

- Sponsoring Org.:
- USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)

- Contributing Org.:
- DES

- OSTI Identifier:
- 1487047

- Report Number(s):
- arXiv:1810.02499; FERMILAB-PUB-18-507-PPD

1697159

- DOE Contract Number:
- AC02-07CH11359

- Resource Type:
- Journal Article

- Journal Name:
- TBD

- Additional Journal Information:
- Journal Name: TBD

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 79 ASTRONOMY AND ASTROPHYSICS; 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS

### Citation Formats

```
Abbott, T. M.C., and et al.
```*Dark Energy Survey Year 1 Results: Constraints on Extended Cosmological Models from Galaxy Clustering and Weak Lensing*. United States: N. p., 2018.
Web.

```
Abbott, T. M.C., & et al.
```*Dark Energy Survey Year 1 Results: Constraints on Extended Cosmological Models from Galaxy Clustering and Weak Lensing*. United States.

```
Abbott, T. M.C., and et al. Thu .
"Dark Energy Survey Year 1 Results: Constraints on Extended Cosmological Models from Galaxy Clustering and Weak Lensing". United States. https://www.osti.gov/servlets/purl/1487047.
```

```
@article{osti_1487047,
```

title = {Dark Energy Survey Year 1 Results: Constraints on Extended Cosmological Models from Galaxy Clustering and Weak Lensing},

author = {Abbott, T. M.C. and et al.},

abstractNote = {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 $N_{\rm eff}$ 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 $\Omega_k=0.0020^{+0.0037}_{-0.0032}$ at the 68\% confidence level, and $N_{\rm eff}<3.28\, (3.55)$ at 68\% (95\%) confidence. For the time-varying equation-of-state, we find the pivot value $(w_p, w_a)=(-0.91^{+0.19}_{-0.23}, -0.57^{+0.93}_{-1.11})$ at pivot redshift $z_p=0.27$ from DES alone, and $(w_p, w_a)=(-1.01^{+0.04}_{-0.04}, -0.28^{+0.37}_{-0.48})$ 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 $\Sigma_0= 0.43^{+0.28}_{-0.29}$ from DES Y1 alone, and $(\Sigma_0, \mu_0)=(0.06^{+0.08}_{-0.07}, -0.11^{+0.42}_{-0.46})$ from DES Y1 combined with external data, consistent with predictions from GR.},

doi = {},

journal = {TBD},

number = ,

volume = ,

place = {United States},

year = {2018},

month = {10}

}

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*Figures/Tables have been extracted from DOE-funded journal article accepted manuscripts.*