Probing gravity with the DES-CMASS sample and BOSS spectroscopy

Abstract

The DES-CMASS sample (DMASS) is designed to optimally combine the weak lensing measurements from the Dark Energy Survey (DES) and redshift-space distortions (RSD) probed by the CMASS galaxy sample from the Baryonic Oscillation Spectroscopic Survey (BOSS). In this paper, we demonstrate the feasibility of adopting DMASS as the equivalent of CMASS for a joint analysis of DES and BOSS in the framework of modified gravity. We utilize the angular clustering of the DMASS galaxies, cosmic shear of the DES metacalibration sources, and cross-correlation of the two as data vectors. By jointly fitting the combination of the data with the RSD measurements from the CMASS sample and Planck data, we obtain the constraints on modified gravity parameters $\mu _0=-0.37^{+0.47}_{-0.45}$ and $\Sigma _0=0.078^{+0.078}_{-0.082}$. Our constraints of modified gravity with DMASS are tighter than those with the DES Year 1 redMaGiC sample with the same external data sets by $29\%$ for μ0 and $21\%$ for Σ0, and comparable to the published results of the DES Year 1 modified gravity analysis despite this work using fewer external data sets. This improvement is mainly because the galaxy bias parameter is shared and more tightly constrained by both CMASS and DMASS, effectively breaking the degeneracy between the galaxy bias and other cosmological parameters. Such an approach to optimally combine photometric and spectroscopic surveys using a photometric sample equivalent to a spectroscopic sample can be applied to combining future surveys having a limited overlap such as DESI and LSST.

Cosmological Tests of Gravity: A Future Perspective

“…The results obtained show a slight deviation from GR when DMASS and CMASS are combined, with µ 0 = −1.23 +0.81 −0.83 and Σ 0 = −0.17 +0.16 −0.15 . However, when Planck data are included in the analysis, the GR limit is consistent with the results, with µ 0 = 0.37 +0.47 −0.45 and Σ 0 = 0.078 +0.078 −0.082 [97]. Other results are available thanks to current data (see, e.g., in [98,99]), but qualitatively the same conclusions can be taken; the GR limit of the parameterized departures used is in agreement with the observational data or has a tension that is not statistically significant ( 2σ).…”

“…In particular, the Dark Energy Survey (DES) collaboration, after its latest data release, has employed a subset of its data, the DMASS galaxy catalog [95], in combination with baryon acoustic oscillations (BAO) and redshift space distortions (RSD) data from CMASS [96], and the CMB data from Planck to further improve the bounds on possible deviations from GR. The analysis performed uses a slightly different parameterization from the one of Equations ( 33) and (34), relying instead on [97]…”

Cosmology with the Roman Space Telescope -- Synergies with CMB lensing

“…This model was used in a series of work recently (see e.g. Lee et al 2021;Abbott et al 2019a;Ferté et al 2019). This form of time dependence is loosely motivated by the heuristic that if the modified gravity model was to explain the recent phase of acceleration, its phenomenology may become important around the same time that the dark energy density does.…”

“…We use GetDist (Lewis 2019) to handle our chains, including enforcing flat prior boundaries and kernel density estimation smoothing of marginalized constraint plots.…”

“…Going beyond the baseline forecast, we also explore different scenarios for the prior calibration of the nuisance parameters, as well as a wide survey scenario that trades off depth for area in the context of combining Roman with the SO data. We also consider extensions to ΛCDM models that include a model-independent modification to the growth of structure 𝜎 8 (𝑧) (Ade et al 2019;García-García et al 2021), a phenomenological model for deviations in the gravitational potentials (Lee et al 2021;Abbott et al 2019a;Ferté et al 2019), and the Hu-Sawicki 𝑓 (𝑅) model (Hu & Sawicki 2007). For our inferred parameter constraints we go beyond a Fisher analysis to capture non-gaussianity in parameter degeneracies.…”