Enhanced lensing rate by clustering of massive galaxies: newly discovered systems in the SLACS fields

Abstract

[Abridged] We exploit the clustering of massive galaxies to perform a high efficiency imaging search for gravitational lenses. Our dataset comprises 44 fields imaged by the Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS), each of which is centered on a lens discovered by the Strong Lens ACS Survey (SLACS). We compare four different search methods: 1) automated detection with the HST Archive Galaxy-scale Gravitational Lens Survey (HAGGLeS) robot, 2) examining cutout images of bright galaxies (BGs) after subtraction of a smooth galaxy light distribution, 3) examining the unsubtracted BG cutouts, and 4) performing a full-frame visual inspection of the ACS images. We compute purity and completeness and consider investigator time for the four algorithms, using the main SLACS lenses as a testbed. The first and second algorithms perform the best. We present the four new lens systems discovered during this comprehensive search, as well as one other likely candidate. For each new lens we use the fundamental plane to estimate the lens velocity dispersion and predict, from the resulting lens geometry, the redshifts of the lensed sources. Two of these new systems are found in galaxy clusters, which include the SLACS lenses in the two respective fields. Overall we find that the enhanced lens abundance (30^{+24}_{-8} lenses/degree^2) is higher than expected for random fields (12^{+4}_{-2} lenses/degree^2 for the COSMOS survey). Additionally, we find that the gravitational lenses we detect are qualitatively different from those in the parent SLACS sample: this imaging survey is largely probing higher-redshift, and lower-mass, early-type galaxies.

submitted to ApJ; 19 pages, 12 figures

References in corpus (17)

• The Sloan Lens ACS Survey. III - The Structure and Formation of Early-type Galaxies and their Evolution since z~1
• The Sloan Lens ACS Survey. IV: the mass density profile of early-type galaxies out to 100 effective radii
• The Sloan Lens ACS Survey. V. The Full ACS Strong-Lens Sample
• The Sloan Lens ACS Survey. VII. Elliptical Galaxy Scaling Laws from Direct Observational Mass Measurements
• The Sloan Lens ACS Survey. VI: Discovery and analysis of a double Einstein ring
• The CFHTLS Strong Lensing Legacy Survey: I. Survey overview and T0002 release sample
• The Sloan Digital Sky Survey Quasar Lens Search. I. Candidate Selection Algorithm
• First catalog of strong lens candidates in the COSMOS field
• The Cosmic Horseshoe: Discovery of an Einstein Ring around a Giant Luminous Red Galaxy
• The Sloan Digital Sky Survey Quasar Lens Search. II. Statistical Lens Sample from the Third Data Release
• Automated detection of galaxy-scale gravitational lenses in high resolution imaging data
• Arcfinder: An algorithm for the automatic detection of gravitational arcs
• Gravitational lenses and lens candidates identified from the COSMOS field
• A Systematic Search for High Surface Brightness Giant Arcs in a Sloan Digital Sky Survey Cluster Sample
• A Strong-Lens Survey in AEGIS: the influence of large scale structure
• A method to search for strong galaxy-galaxy lenses in optical imaging surveys
• Three Gravitational Lenses for the Price of One: Enhanced Strong Lensing through Galaxy Clustering

Cited by in corpus (6)

• Strong Lensing by Galaxies
• RingFinder: automated detection of galaxy-scale gravitational lenses in ground-based multi-filter imaging data
• Survey of Gravitationally-lensed Objects in HSC Imaging (SuGOHI). II. Environments and Line-of-Sight Structure of Strong Gravitational Lens Galaxies to z ~ 0.8
• A seven square degrees survey for galaxy-scale gravitational lenses with the HST imaging archive
• A search for edge-on galaxy lenses in the CFHT Legacy Survey
• Extensive light profile fitting of galaxy-scale strong lenses