Galaxy-Galaxy Lensing in the DES Science Verification Data

TL;DR

This paper presents galaxy-galaxy lensing measurements from DES SV data, demonstrating high signal-to-noise results, consistency across pipelines, and constraints on galaxy halo masses, aiding future cosmological studies.

Contribution

First detailed galaxy-galaxy lensing analysis using DES SV data with rigorous systematics checks and HOD modeling to constrain galaxy halo masses.

Findings

High signal-to-noise lensing measurement (S/N=29)

No evidence for halo mass evolution with redshift

Consistent results across two shear measurement pipelines

Abstract

We present galaxy-galaxy lensing results from 139 square degrees of Dark Energy Survey (DES) Science Verification (SV) data. Our lens sample consists of red galaxies, known as redMaGiC, which are specifically selected to have a low photometric redshift error and outlier rate. The lensing measurement has a total signal-to-noise of 29 over scales $0.09 < R < 15$ Mpc/$h$, including all lenses over a wide redshift range $0.2 < z < 0.8$. Dividing the lenses into three redshift bins for this constant moving number density sample, we find no evidence for evolution in the halo mass with redshift. We obtain consistent results for the lensing measurement with two independent shear pipelines, ngmix and im3shape. We perform a number of null tests on the shear and photometric redshift catalogs and quantify resulting systematic uncertainties. Covariances from jackknife subsamples of the data are validated with a suite of 50 mock surveys. The results and systematics checks in this work provide a critical input for future cosmological and galaxy evolution studies with the DES data and redMaGiC galaxy samples. We fit a Halo Occupation Distribution (HOD) model, and demonstrate that our data constrains the mean halo mass of the lens galaxies, despite strong degeneracies between individual HOD parameters.