CFHTLS TeraPix T0004 Release
T0004 is now world-wide public
Catalog Update Information:
During the Fall/Winter of 2007/2008 the CFHTLS data processing team
(CFHT/Terapix/CADC) became aware of irregularities in the computed
magnitude uncertainties in some CFHTLS T0004 catalogues. For some
objects errors were a factor 3 to 7 smaller than the real values.
The catalogues were corrected and updated at CADC by September 2007.
However an unexpected and unfortunate series of unrelated technical
problems at CADC and at Terapix occurred over the period September to
January while we were attempting to release the corrected catalogues:
disk failures at Terapix and CADC that corrupted some compressed
catalogues, then a subtle bug in the automated Terapix-to-CADC catalogue
control and update process, and finally a human error that led the old
versions of the catalogues to be put back on-line instead of the new
ones. All these problems corrupted, in different ways and at different
times, the new catalogues, leading to unreliable files (which were
unfortunately still available to users to download over that period).
It took several months to fix this string of problems and check the
catalogues, which are now are finally stable and ready for delivery to
users. The error estimates corrected in September 2007 are now part of
the finally correct release of the T0004 catalogues that occurred on
January 2008. These catalogues are identical as the early T0004 except
for the magnitude error estimates which are now set to correct values.
In order to improve the reliability of the data transferred between CFHT
to CADC, CADC to Terapix and CADC to users, CADC implemented a new
system for handling failed transfers so that the particular problem, and
others, will not occur in the future. Furthermore, it was decided to
include a checksum. The CADC now provides (from the 'Stack Groups'
download pages) the MD5 checksum of all CFHTLS data products, to aid
CFHTLS users in knowing which versions of the catalogues they have
downloaded. MD5 software is available on most LINUX system (try: man
md5) and users should compare the locally computed value of the MD5 sum
to the value listed on the 'Stack Groups' pages. The Stack Group
pages are best accessed via the page:
Terapix Stacks Search Form and can also be access directly via the page:
Terapix Stacks Retrieval Form
Single Click Download
Follow this link to download the ENTIRE T0004 RELEASE (2752 files, ~ 1.5Tbytes), this query can take up-to 5 minutes to execute. We strongly recommend that you use information below to select
particular parts of the T0004 release, the Search Form option is
particularly good at
limiting the content to the specific files of interest.
Search Form
Use the stack search form to locate particular
subsets (by filter, exposure depth, image quality etc.) of the DEEP and/or Wide fields available or follow the links in the table below.
DEEP
Release T0004 from of the CFHTLS Stacks consists two (2) sets of stacks for each of the 4 deep pointings. One stack is made with the images take in the best 25% (D-25) of image quality and one with the best 85% (D-85), resulting in 8 DEEP stack sets. For each stack set, Terapix provides an image, catalog, and weight-map for each filter and also provides a chi2 and mask image for each field. The entire collection of all DEEP images and catalogs can be retrieved by following the 'DEEP' link in the table below.
Wide
For the 'Wide' survey fields (Wide-1,2,3,4) a selection of imaging data have been used to provide images, catalogs, masks and weight-maps have been produced. For those fields that have been imaged in the g', r' and i' filters a chi2 image has also been produce. The complete set of Wide images and catalogs can be retrieved by clicking on the name of the survey below.
Summary
During the Wide survey each patch is imaged in u/g/r/i/z. Images presenting the T0004 sky coverage for each patch/filter are avaiable from Terapix: Wide-1, Wide-2, Wide-3, Wide-4 Below is a summary table providing the area coverage of each of the Wide and Deep survey fields. The name of each of the surveys links to a page that allows you to retrieve all the data associated with that survey. The area-coverage values links to a form that will allow you to retrieve just the files associated with the paritcular filter.
| Survey | u | g | r | i | z |
|---|---|---|---|---|---|
| DEEP | 8 | 8 | 8 | 8 | 8 |
| Wide 1 | 19 | 54 | 71 | 44 | 20 |
| Wide 2 | N/A | 20 | 39 | 33 | 1 |
| Wide 3 | 5 | 43 | 47 | 44 | 13 |
| Wide 4 | 11 | 16 | 16 | 16 | 12 |
