ARCLETS (Analysis of Realistic Cluster Lensing through Extensive Training Simulations)


The evolution of the cluster mass function is a powerful test of cosmology. Success in extracting the cosmological information depends on accurate and unbiased determination of the mass via gravitational lensing. Although much progress has been made in validating algorithms in weak gravitational lensing, all of the studies have been in the context of gravitational lensing measurements of cosmic shear. Our goal is to validate and improve algorithms for measuring the lensing signal in the cluster environment to reach the goal of 1% accurate mass reconstruction (when averaged over many clusters) for clusters spanning the redshift range 0.1 < z < 1.1. We aim to do so via construction of a suite of simulations aimed at testing different aspects of cluster mass measurement.

Guiding Principles

The extraction of the mass of a cluster of galaxies from multi-epoch, multi-band optical data is a complicated process, with many interlocking components. Algorithms are required to detect galaxies, deblend isophotes of overlapping objects, select stars to determine the point spread function, measure the point spread function variation with position and time, estimate galaxy redshifts, interpolate the PSF to the position of the galaxies, correct for the smearing of the galaxies by the telescope and atmosphere, measure the projected mass distribution, account for projection effects and the effect of mass substructure and other structures along the line of sight. To make progress in measurement, we seek to break down the problem into component steps and build up a sequence of simulations of increasing realism (and hence complexity). We start simple in order to isolate areas where algorithms need further development. We plan to release new simulaition suites roughly twice a year, with a goal of fully validating cluster mass algorithms in preparation for LSST .

Who we are

These simulations are being produced under the auspices of the Clusters Working group of the LSST Dark Energy Science Collaboration (DESC). The current and past members of the simulations and validation team are listed at We anticipate that these results will have an important use beyond the LSST DESC, both because other upcoming projects will measure galaxy clusters (EUCLID, WFIRST) and because there are current datasets that can benefit from validation of the code (DES, HSC, CFHTLS, etc). Therefore, we produce simulations that produce appropriate conditions for multiple telescopes as part of the data release process.

RELEASE 1 (Release March 31, 2014, closing Jaunary 1, 2014)