Terapix Star Formation Region IC 1396, © 2002 CFHT
Planned CFHTLS-Wide Observations for semesters 05A
by HAU - Updated August 31st, 2005

With the flip of the L3 lens of the WFC, the MegaPrime/MegaCam system now delivers data that allow for attaining the Wide Synoptic Survey goals. There is no reason to hold back the Wide scheduling anymore, and the observations of the survey should resume to their normal pace. This has been agreed within the Steering Group where it was decided that each of the survey component would receive their nominal share in 05A. Assuming an efficiency of 4.7 hours per night, and 50 nights of CFHTLS observations, we can reasonably expect to gather 80.0 hours of data for the Wide component.

The scheduling of the semester 05A observations has been made with the following constraints:

  • The area coverage needs to increase fast for the Cosmic Shear science.
  • If the survey ends in 08A (nominal duration of the survey), we need to finish gathering the first epoch of r band data before the end of 06A. This calls for fast area coverage in r.
  • u and z band data is needed for galaxy and clusters studies.

Point 3 is in conflict with points 1 and 2. This is clearly seen in table 1 where the amount of time needed to cover a Wide pointing in both g, r/2 and i is 2.3 hours, against 1.8 hours in u* and 2.1 in z (the notation r/2 signify that half the final exposure time in r is gathered). After consultation with the user base of the CFHTLS (cfhtls-w mailing list), we decided to schedule 42.75 hrs on W3 to gather g, r/2 and i only, hence covering a large area, and 37.25 hours in u*/2, g, r/2, i, z/2 on W2. Moreover, a pointing in W2 (w2.+2+2) will receive its full depth in u* and z

The expected coverage in each of the fields is plotted below, to be compared to their actual coverage at the end of 04B. By the end of 05A, we expect about 28 square degrees will be available for weak lensing studies in W3 and 13 in W2, while 13 square degrees in W2 will be available for clusters studies, although with shallower depth in u* and z.

Planned coverage of W2 at the end of 05A - 28.2 kb
Planned coverage of W2 at the end of 05A
See this article for an explanation of the legend of this figure. The planned coverage was made assuming the W2 field would be observed for 37.25 hours

Planned coverage of W3 at the end of 05A - 39.6 kb
Planned coverage of W3 at the end of 05A
See this article for an explanation of the legend of this figure. The planned coverage was made assuming the W3 field would be observed for 42.75 hours.

Comments ? Questions ? Herve Aussel email - 340 bytes


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