The CFHT Legacy Survey: Done!

Veillet, Christian

The CFHT Legacy Survey (CFHTLS) was first presented at ADASS XIII in 2003. MegaCam, then a new one sq.deg. 340-Megapixel wide-field CCD mosaic camera freshly installed on a new upper-end with new optics, was only in its first months of operation. The CFHTLS had been allocated 500 nights with specific goals, all exciting and challenging, aimed at the study of the Kuiper Belt through a very-wide survey of the Ecliptic, of the large scale structure of the Universe through weak lensing, and of its acceleration thanks to the detection and follow-up of Type-Ia SNe in four deep fields.

The CFHTLS is now completed and its final public data release (images, stacks and catalogues) will happen right after ADASS XX: a good opportunity to reflect on what worked and what did not, as the real world made some of the initial assumptions look more like dreams than reasonable expectations. The presentation will focus on the lessons learned, from the need for flexibility in spite of careful a-priori planning to the importance of clear priorities when a survey is cohabitating with regular PI programs. It will also stress the paramount role played by the queued service observing and the data pre-processing handled by the observatory staff, nicely reciprocated by the impact of the CFHTLS on the scientific visibility of CFHT, as well as by the remarkable characterization of MegaCam and the fine-tuning of its image processing made by and for the survey direct users, which benefited the whole users of MegaCam, all communities included. The most important results of the CFHTLS will be highlighted; some of them come from the use of the CFHT Archive, already showing its legacy value. The new Large Programs, which started at CFHT once the CFHTLS observations were completed, will be briefly described.

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