CMB lensing tomography with the DES Science Verification galaxies

Abstract

We measure the cross-correlation between the galaxy density in the Dark Energy Survey (DES) Science Verification data and the lensing of the cosmic microwave background (CMB) as reconstructed with the Planck satellite and the South Pole Telescope (SPT). When using the DES main galaxy sample over the full redshift range 0.2 < z phot < 1.2, a cross-correlation signal is detected at 6σ and 4σ with SPT and Planck respectively. We then divide the DES galaxies into five photometric redshift bins, finding significant (>2σ) detections in all bins. Comparing to the fiducial Planck cosmology, we find the redshift evolution of the signal matches expectations, although the amplitude is consistently lower than predicted across redshift bins. We test for possible systematics that could affect our result and find no evidence for significant contamination. Finally, we demonstrate how these measurements can be used to constrain the growth of structure across cosmic time. We find the data are fit by a model in which the amplitude of structure in the z < 1.2 universe is 0.73 ± 0.16 times as large as predicted in the ΛCDM Planck cosmology, a 1.7σ deviation.

Joint measurement of lensing–galaxy correlations using SPT and DES SV data

“…The galaxy shear catalog used in this work was extensively tested in Jarvis et al (2015), while galaxy-galaxy lensing measurements and systematics tests were performed in Clampitt et al (2016). Additionally, the cross-correlation between the galaxy catalog used in this work and the SPT-derived CMB κ map was first measured in Giannantonio et al (2016). These and other DES SV papers provided key methodological ingredients that support the analysis presented here.…”

“…As demonstrated in Giannantonio et al (2016), the signal-to-noise of w κg (θ) measured using the benchmark galaxies and the Planck κ map is only slightly lower than the signal-to-noise of the same measurement using the SPT κ map. However, because this work is intended as a "proof of concept" for the joint w κg (θ) and w γ T g (θ) measurement, we postpone a joint measurement of w κg (θ) and w γ T g (θ) with Planck and DES data to future work based on a larger DES sample.…”

“…In general, though, DES SV science results have been shown to be quite robust to the choice of photo-z estimation code (e.g. Giannantonio et al 2016;Crocce et al 2016). Tracer and source galaxies are selected on the basis of the z value at which p(z) peaks, z p .…”

“…The CMB κ map was pixelized using a Healpix (Górski et al 2005) grid with N side = 2048. The processed SPT CMB lensing maps used here are identical to those used in Giannantonio et al (2016) and we refer the reader to that work for more details. The same maps were also used in the cross-correlation of CMB lensing with galaxy lensing measurement of Kirk et al (2015).…”

“…The same maps were also used in the cross-correlation of CMB lensing with galaxy lensing measurement of Kirk et al (2015). As in Giannantonio et al (2016), we filter the pixelized CMB κ map to remove modes with ℓ < 30 and also apply Gaussianbeam smoothing with θFWHM = 5.4 ′ . In our analysis, we use the CMB κ map across the full SPT-E region without applying any additional masking.…”