STEP: Data
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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 please first discuss your findings through the STEP mailing list to give the original owners of the data a chance to respond and collaborate.

VLT Data:

  • From Yannick, Ludo and Elisabetta, there is the VLT data obtained with the FORS instrument (Maoli et al), available for cosmic shear testing,
  • You can get the data on the ftp anonymous site, in the pub/VLTshear directory. It contains the following directories: vlt_catalogs , vlt_images , vlt_masks
  • The images are the final stacked data only (individual images will be provided in a next step, if needed).
  • The catalogues are the SExtractor catalogues generated by Elisabetta Semboloni who measured the E and B modes in the VLT data (and found zero signal for the B-modes).
  • The masks contain the polygons as well as the ellipses of each object detected. The masks have been written in the SAOimage format (not DS9). Each contains at least masks for the periphery and for the central cross that masks the low S/N area produced by 4 outputs used to read the CCD (4 quadrants read).
  • Click here for summary and references, target positions on the sky, target positions and finding charts and summary of each stacked image. For details of each stacked image click on target indent.

COMBO-17 Data:

  • The COMBO-17 team have made deep R-band data, obtained with the WFI instrument, available for cosmic shear testing. This data set contains 5 30x30 arcminute fields; 4 'blank fields' plus the A901 super-cluster field analysed in Gray et. al. 2002. Details of the COMBO-17 cosmic shear analysis can be found in Brown et. al. 2003.
  • You can download the data from The pub/COMBO/STEP directory contains the following images:
    A901 super-cluster field a901R_8k.fits
    Chandra Deep Field South cdfR_8k.fits
    FORS deep field fdfR_8k.fits
    s11 field s11R_8k.fits
    South Galactic Pole sgpR_8k.fits
  • The images are the final stacked data. Each CCD chip has been separately reduced and the recombined to produce the final 8k (quarter square degree) fits image. Note that the WFI camera has 8 chips that are arranged in an 4x2 formation (see Brown et. al. 2003 for details).
  • Click here for target positions

Coming soon: Archive WFI data

Last modified 1st Nov.
STEP pages maintained by Catherine Heymans: heymans[at]