Final CFHTLS TERAPIX dataset available at CALET

By | October 4, 2018

The Canada-France-Hawaii Telescope Legacy survey, or CFHTLS, was a wide-field survey sky-survey carried out using the Megacam camera on CFHT. CFHTLS had two components: a “wide” and “deep” survey. The deep survey comprised four deep fields observed in ugriz bands and the wide survey was a shallower survey covering around 140 square degrees in five bands. At the time, CFHTLS was unique, providing an unrivalled combination of depth, areal coverage and image quality, reaching around out to around redshift. It would take at almost a decade until it was surpassed by new instruments on other telescopes.

CFHTLS Deep (D) and Wide (W) survey fields (courtesy CFHT)

A lot of landmark science came out of the CFHTLS data; the primary goals were weak lensing (CFHTLens) and a supernovae survey (the SLS). Between them these surveys have gained thousands of citations, providing new and stringent constraints on our cosmological model and pointing the way towards future surveys like Euclid. The release has been described in this proceedings paper.

One of the primary objectives of the TERAPIX data centre was to process MEGACAM data taken for the CFHTLS starting from pre-reduced data produced by CFHT and provide it to the community together with data quality control assessments and catalogues. Although CFHTLS data products have been archived at CDS and CADC a few TERAPIX data products and in particular quality assessments were not been archived. They only exist on computers on the IAP basement which were once part TERAPIX– but TERAPIX operation ceased in 2017. Some of these computers (although still operational) are now more than ten years old and are no longer maintained. Thus the risk of losing this dataset was not negligible.

Part of the CFHTLS “D3” deep field (CFHT/Coleum)

One important mission of the CALET project is to preserve the work which had been done at TERAPIX. To this end, we have transferred the last and final TERAPIX CFHTLS release to CALET computers (the CANDIDE cluster) and are now making it available to the community. We have replicated the old TERAPIX CFHTLS release page (in all its early 2000s glory), and the links on this page also point towards TERAPIX-produced data quality control products. We are also currently mirroring the TERAPIX web server on CANDIDE computers. Here are the links:

Find the TERAPIX CFHTLS T07 release page here
Find the TERAPIX CFHTLS explanatory document here

Of course, this is only a temporary solution. CANDIDE, the CALET computer cluser is not an archive system, and it was not meant to be. So it is important find a permanent, archival facility for this dataset. For this reason we are collaborating with the Integrated data and operations centre (IDOC) at IAS, Orsay to find a permanent home for this and future data products from CALET. Stay tuned.

Acknowledgements CALET has been made possible thanks to equipment grants from Dim-ACAV project (Le Domaine d’Intérêt Majeur ACAV), Le Programme National de Cosmologie et Galaxies and the CSAA.

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