STEP: Shear TEsting Programme
STEP home Simulations Data Mailing List STEP Workshop

The Shear TEsting Programme, STEP, is a forum where people can test methods on a series of public image simulations, exchange data for cosmic shear analysis and share technical knowledge. STEP is now in its third year and is evolving into GREAT08; GRavitational lEnsing Accuracy Testing 2008. The GREAT08 PASCAL challenge, is based on STEP4 but is being developed specifically for the statistical machine learning community. For more information see the GREAT08 wiki or contact the PI Sarah Bridle.

STEP 1: Analysis of simulated ground-based observations. Status : Complete

In the first STEP project a series of different weak lensing methods were used to analyse a set of SkyMaker simulations of ground based observations and a smaller set of Shapelet simulations . The analysis summary report is online along with the minutes of the December post-analysis STEP telecon. The first STEP paper which documents the results from the analysis of the SkyMaker simulations can be found here.

STEP 2: Assessing the impact of complex galaxy morphologies with shapelet simulations. Status : Complete

In the second STEP project a series of different weak lensing methods were used to analyse a set of Shapelet simulations of ground based observations. These simulations have allowed us to assess the impact of galaxy morphology on our weak lensing analyses. We have also tested a more complex set of PSFs. The detailed results of the STEP2 analysis are online along with the minutes of the April STEP2 telecon. The input shears and catalogues can be downloaded. The second STEP paper which documents the results from the analysis of the Shapelet simulations can be found here.

STEP 3: Space-based observations. Status : Results online

The results of the blind analysis of Shapelet simulations of space-based data are now online. Information about downloading the spaceSTEP simulations, can be found here.
If you would like to join the space-based subgroup of STEP please contact Catherine.

STEP 4: Several simple steps. Status : Stage 1 online

The first stage of the STEP4 project is now available for download. These simulations will test to high precision the ability to measure shear for large galaxies (galaxy fwhm = 2x PSF fwhm) at different signal-to-noise levels. We plan to follow this first stage with progressively more complex simulations as discussed on the stepwiki webpage.

Mirror STEP Status : Simulations online

Jes Ford and Jason Rhodes have developed a series of image simulations that test the impact of mirror size on shear measurement accuracy. These simulations are available for download until December 5th 2007. For more information see the Mirror STEP webpage.

Data STEP

  • The data that is currently available for cosmic shear tests (VLT and COMBO-17) can be found here .
  • If you wish to make your own data available please send details to heymans[at]physics.ubc.ca such that the website can be updated.

Please note that data made available through STEP is for testing cosmic shear analysis only. If you wish to make use of the data for other purposes contact the PIs of each survey. If you wish to publish cosmic shear results from STEP data you should first discuss your findings through the STEP mailing list to give the original owners of the data a chance to respond and collaborate.

Last modified 16th Nov.
STEP pages maintained by Catherine Heymans: heymans[at]physics.ubc.ca