The X-Shooter Lens Survey - II. Sample presentation and spatially-resolved kinematics

Abstract

We present the X-Shooter Lens Survey (XLENS) data. The main goal of XLENS is to disentangle the stellar and dark matter content of massive early-type galaxies (ETGs), through combined strong gravitational lensing, dynamics and spectroscopic stellar population studies. The sample consists of 11 lens galaxies covering the redshift range from 0.1 to 0.45 and having stellar velocity dispersions between 250 and 380 km s-1. All galaxies have multiband, highquality HST imaging. We have obtained long-slit spectra of the lens galaxies with X-Shooter on the VLT.We are able to disentangle the dark and luminous mass components by combining lensing and extended kinematics data sets, and we are also able to precisely constrain stellar mass-to-light ratios and infer the value of the low-mass cut-off of the initial mass functions (IMF), by adding spectroscopic stellar population information. Our goal is to correlate these IMF parameters with ETG masses and investigate the relation between baryonic and nonbaryonic matter during the mass assembly and structure formation processes. In this paper, we provide an overview of the survey, highlighting its scientific motivations, main goals and techniques. We present the current sample, briefly describing the data reduction and analysis process, and we present the first results on spatially-resolved kinematics.