Information on resource 'CARS survey data'
Images and data from from the CFHTLS archive research survey, a
multi-band dataset spanning 37 square degrees of sky in high galactic
latitudes.
These services deliver products from the CFHTLS-Archive-Research Survey
(CARS). The survey currently offers derived products from 37
sq. degrees of the Wide part from the Canada-France-Hawaii Telescope
Legacy Survey (CFHTLS). The main documentation for the products, its
creation and its content is the publication 2009A&A...493.1197E.
Here, we discuss some points which are not evident from this publication.
AVAILABLE DATA PRODUCTS
For each 1 sq. deg. CARS pointing we currently offer the following products
(we discuss them on the example of the CARS pointing W1m0p1); a typical file
is named W1m0p1_izrgu.V1.7A.final.cat. The name contains the following
information:
- W1m0p1 -- name of CARS field under consideration
- izrgu -- filters involved in the product (here i', r', z', g', u*);
for catalogues etc. the first listed filter corresponds to
the object detection filter (here 'i'; see also 2009A&A...493.1197E)
- V1.7A -- internal CARS version number
- final -- 'final' product
The individual files we offer are:
- W1m0p1_izrgu.V1.7A.final.cat
- object catalogue in FITS binary format; beware that they are very
big and cumbersome to handle if you do not have efficient tools to
work on big FITS binary tables! (typical file size per field: 0.5GB!)
- W1m0p1_izrgu.V1.7A.final.asc.gz
- An ASCII version of W1m0p1_izrgu.V1.7A.final.cat containing a subset
of the most important catalogue quantities. This catalogue should be
sufficient for most users. The main content of the catalogue can
also be queried in the cat service.
(typical gzipped file size per field: 20MB)
- W1m0p1_izrgu.V1.7A.final.reg.gz
An ASCII ds9 region file containing saoimage/ds9 polygon entries
(in pixel coordinates). They represent the CARS image masks described
in Sect. 3.4 of 2009A&A...493.1197E. Polygons originating from different
masking procedures are encoded with different colours (look at
expressions such as '# color=yellow' at the end of each line).
We offer this file so that interested users can construct own masks
containing only parts of our global MASK key. (typical gzipped file size
per field: 1MB)
The colour coding in these files is as follows:
- yellow: masks from our object density analysis and stars identified
in the USNO-A2 catalogue
- green: stars identified in the GSC1 and GSC2 cataogues
- magenta: masks around extended haloes of bright stars
- red: masks from our asteroid track analysis
W1m0p1_irg.V1.7A.truecol.jpg
low resolution true colour i', r' and g' JPG image of the CARS field.
These images allow a quick look at the data but they are probably not
suitable for high-quality poster print-outs. (typical file size per field:
10MB)
- W1m0p1_izrgu.V1.7A.masks.obj.jpg
low resolution JPG image showing object positions and object masks
overlayed on the i'-band image. It allows a quick-look at field-layout
and object positions. (typical file size per field: 3MB)
The colour coding in this is:
- green: areas excluded from scientific analysis by our MASK key
- yellow: stellar sources (SExtractor CLASS_STAR >=0.95)
- red: galaxies with high-confidence photo-z estimates:
(SExtractor CLASS_STAR < 0.95; reliable object photometry
in five bands; BPZ ODDS quality parameter > 0.9);
see also Sect. 4 of 2009A&A...493.1197E
- blue: all other galaxies (SExtractor CLASS_STAR < 0.95)
CATALOGUE QUANTITIES
See 2009A&A...493.1197E, in particular Sect. 4, and the SExtractor Users manual
for a description of most catalogue entries. Also see the table notes.
CURRENT COVERAGE
Services defined within this resource descriptor
Tables defined within this resource descriptor
- cars.cats
Metadata for CARS
object catalogues in FITS binary format; beware that they are very
big and cumbersome to handle if you do not have efficient tools to
work on big FITS binary tables! (typical file size per field: 0.5GB)
- cars.images – queryable through TAP and ADQL
Metadata for co-added CFHTLS archive images
used for producing the CARS source list (cars.srccat).
- cars.masks
Metadata for low resolution JPG images showing object positions and object
masks overlayed on the CARS i'-band image. It allows a quick-look at
field-layout and object positions. (typical file size per field: 3MB)
The colour coding in this is:
- green: areas excluded from scientific analysis by our MASK key
- yellow: stellar sources (SExtractor CLASS_STAR >=0.95)
- red: galaxies with high-confidence photo-z estimates:
(SExtractor CLASS_STAR < 0.95; reliable object photometry
in five bands; BPZ ODDS quality parameter > 0.9);
see also Sect. 4 of 2009A&A...493.1197E.
- blue: all other galaxies (SExtractor CLASS_STAR < 0.95)
- cars.products
A view combining most of the CARS-related products.
- cars.regions
Metadata for CARS region files.
An ASCII ds9 region file containing saoimage/ds9 polygon entries
(in pixel coordinates). They represent the CARS image masks described
in Sect. 3.4 of 2009A&A...493.1197E. Polygons originating from different
masking procedures are encoded with different colours (look at
expressions such as '# color=yellow' at the end of each line).
We offer this file so that interested users can construct own masks
containing only parts of our global MASK key. (typical gzipped file size per field: 1MB)
The colour coding in these files is as follows:
- yellow: masks from our object density analysis and stars identified
in the USNO-A2 catalogue
- green: stars identified in the GSC1 and GSC2 cataogues
- magenta: masks around extended haloes of bright stars
- red: masks from our asteroid track analysis
- cars.srccat – queryable through TAP and ADQL
Extracted sources from the CARS survey, comprising positions and
multiband photometry.
- cars.truecol
Metadata for low resolution true colour i', r' and g' JPG images of the CARS
fields. These images allow a quick look at the data but they are probably
not suitable for high-quality poster print-outs. (typical file size per
field: 10MB)
- cars.weights
Copyright, License, Acknowledgements
If you use the CARS products for your own research,
please give proper acknowledgment to
CADC, the
CFHTLS project and the
publication 2009A&A...493.1197E
[Manage RD]
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