The order of magnitude increase in volume probed by LSST will open a new phase of strong lensing science, by enabling statistical studies to be carried out for a wide range of applications. The LSST SL science goals are best summarised in the LSST Science Book v2.0 (access the Strong Lensing chapter directly here).
Currently, the SL science collaboration & DESC-SLTT work is focused on accurate measurement of time delays from LSST light curves, simulating time-delay systems and developing analysis tools. We are experimenting with novel ways to find and model lenses but there's much work to be done. The bulk of the new LSST lenses discovered will require high resolution imaging and spectroscopic confirmation that will be the domain of space- and ground-based telescopes.
The following list encapsulates 10 high priority science goals identified by the SLSC, however this list is by no means exhaustive and we welcome contributions on further interest areas.
Detailed Modelling of Time Delay Lenses and Their Environments: Galaxy Properties and H0Dt
Statistical Approaches to H0Dt from Lens Time Delays
Galaxy and Group-scale Mass Distributions, and their Evolution
Sub-galactic CDM Structure from Flux Ratio Statistics
Accretion Disk Structure from 1000 Microlensed AGN
Measuring the Physical Properties and Rates of High Redshift SNe with a Large Array of Cosmic Telescopes
Cluster Properties and Cosmography from Arc Statistics
Calibrating the LSST Cluster Mass Function using Strong and Weak Lensing
Exotic Gravitational Lenses in the LSST Survey
Multiply-imaged Gamma Ray Bursts
Main activities involve preparing for the phase change from detailed studies of individual systems to statistically large samples:
How do we find strong lens samples with good completeness and purity?
How do we accurately and efficiently analyze large samples of lenses for key SLWG/SLSC science goals?
How do we create reliable lens models for large samples? How accurate is automated lens modeling and what are the limitations?
What is the best means of acquiring supplementary data on large samples of strong lenses?
We are currently compiling tasks for the Strong Lensing Science Roadmap. This is highly complementary to the DESC Science Road Map (SRM) and focusses on non DE activities as well as those that are common to the SL part of the DESC SRM. This is also linked to the Galaxies Science Roadmap. To get involved in these activities please contact us.
Complementarity to DESC-SL TT activities
The DESC-Strong Lensing Topical team (DESC-SL TT) activities are focussed on time-delay cosmography from lensed quasars and supernovae, and distance measures from compound lenses. Section 3.4 of the DESC SRM lays out the tasks envisaged to deliver these split by analysis steps. Several activities have strong overlap with the SLSC goals (e.g. Lens finding methods SLFinder, the monitor that extract light curves SLMonitor, inferring time delays SLTimer, and the steps to characterise the Lens environments SLEnvCounter & SLMassMapper). Each require software & infrastructure to be built including understanding systematic uncertainties e.g. from poor extraction of photometry in blended regions and their impact on extracted light curves and characterising the environment in both the lens plane and the line of sight. Lens finding in a survey of such large volume remains untested for which it is important to understand the selection effects of various methods.
The focus of DESC work to date has been on data challenges, embarking on the DESC data challenge 2 (DC2) creating realistic datasets and analysis tools to simulates SL science to be extracted from LSST data sets. See further information from:
the DESC website http://lsst-desc.org/ including the DESC white paper that lead to the DESC SRM and describe DC2
Twinkles is a joint open project to develop sky simulations (images and catalogues) for LSST to search for SNe and gravitational lens time delays between the DESC SL and SNe working groups
The first time delay challenge (http://timedelaychallenge.org/) was set-up to perform a blind analysis of simulated light curves of SL quasars community teams were asked to infer the delays that went into them. The experimental design and results are available in http://arxiv.org/abs/1310.4830 & http://arxiv.org/abs/1409.1254, respectively.
We encourage our members to join both Science Collaborations to benefit and best work together.