CFHTLS Overview
Canada and France joined a large fraction (~50%) of their dark
and grey telescope time from mid-2003 to early 2009 for a large project,
the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS).
The data acquisition and calibration has been a major undertaking for
the Canadian and French communities: more than 2300 hours over 5 years
(an equivalent of 450 nights) have been devoted to the survey using the
wide field optical imaging camera MegaCam, a 1 degree by 1 degree field
of view 340 Megapixel camera.
Current Data Release
The Terapix
CFHTLS T0005 release of finely calibrated stacks and catalogs is available
to the worldwide community at the Canadian Astronomy Data Centre (since the 14th of November 2009).
The CFHTLS T0005 release includes the vast majority of data gathered over the course of the CFHT Legacy Survey.
The Terapix
CFHTLS T0006 release of stacks and catalogs offers for the first time the complete CFHTLS data set,
it will be made available to the worldwide community in November 2010 (it has already been released to
the two CFHTLS communities under the standard 1 year proprietary data policy). There is still an extensive calibration effort going on in the CFHTLS
community for the next planned (and arguably last) release of the survey (T0007). For those interested in
the individual frames, the vast majority of the 22,000 pre-processed and calibrated CFHT's Elixir
images is now open to the worldwide community at the
CADC.
Please note the acknowledgment text for publications when using CFHTLS (archived or proprietary) data.
Three surveys from the Solar System to the Distant Universe
The supernovae survey and the deep synoptic survey: SNLS and the "Deep"
Covering 4 square degrees in four independent fields spread across
the sky to have two fields visible throughout a given night at any time of the year,
and acquired through the whole filter set (u*, g', r', i', z') with integration
times ranging from 33 to 132 hours depending on the filter
(u*: 33, g':33, r':66, i':132, z':66), this survey was
sequenced over 5 years for the SuperNovae Legacy Survey (SNLS):
aimed mainly at the detection and monitoring of as many as
500 type Ia supernovae and at the study of the galaxy
distribution on images reaching r'=28, this survey is leading to a better
understanding of the early universe as well as a the determination of the dark
energy parameters with an unprecedented accuracy. The galaxies and quasars
constitute statistical samples bringing strong constraints on
galaxy evolution and global star formation history. Thanks to the time sequencing,
transient phenomena and moving objects can be detected, providing a unique
monitoring over five years of fields at various galactic and ecliptic latitudes.
A wide synoptic survey, the "Wide"
Covering 170 square degrees in four patches of 25 to 72
square degrees through the whole filter set (u*, g', r', i', z') down to i'=24.5,
this survey allows the study of the large scale structures and matter
distribution in the universe through weak lensing and galaxy distribution,
as well as the study of clusters of galaxies through morphology and photometric
properties of galaxies.
Thanks to the sequencing of the r' observations in two phases, early in
the survey and three years later, proper motions are available for
galactic structure studies. All fields are to be used for stellar population
investigations and searched for moving objects and transient phenomena.
A very wide shallow survey, the "Very Wide"
Covering a large fraction of the ecliptic plane inside a band of +/-2 degrees
for a total area of 410 square degrees, this survey provides an unprecedented
sample of the solar system population beyond Neptune. This data set provided
discoveries that challenge the currently discussed models of the solar system
formation. CFHTLS-VW was conducted in 3 colors (g'/r'/i') to create a
new stellar data set for studies related to stellar populations (including
white and brown dwarfs), as well as structures & dynamics of our Galaxy.
Survey Organization
The three main entities serving the Canadian and French communities are 1) the CFHT for
the data acquisition, pre-processing and calibration, 2) Terapix (based at the Institut
d'Astrophysique de Paris - IAP) for the data ressampling and stacking, fine astrometric
and photometric calibration, and source catalogs generation, 3) the Canadian Astronomy
Data Centre (CADC, based at the Herzberg Institute of Astrophysics in Victoria) for all
activities related to the archiving and release of the various data products to the
scientific community.
The CFHT Board of Executives gave its final approval for the project following a
SAC recommendation prepared
at its May 2002 meeting. Various reports and recommendations have been written
in the course of the year 2001 and, though a bit dated today, they still contain
the core rational for the survey. The documents are presented
here.
The Canada-France-Hawaii Telescope Legacy Survey was conducted
under the supervision of the CFHT Scientific Advisory Council (SAC),
organized and monitored by a Steering Group (SG), and technically
supported by a Data Oversight Group (DOG).
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