Information on Service 'CARS image cutouts'

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Further access options are discussed below

Images and data from from the CFHTLS archive research survey, a multi-band dataset spanning 37 square degrees of sky in high galactic latitudes.

For a list of all services and tables belonging to this service's resource, see Information on resource 'CARS survey data'

Service Documentation

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:

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

CARS coverage

Overview

You can access this service using:

This service is published as follows:

local means it is listed on our front page, ivo_managed means it has a record in the VO registry.

Other services provided on the underlying data include:

Input Fields

The following fields are available to provide input to the service (with some renderers, some of these fields may be unavailable):

NameTable Head DescriptionUnitUCD
cutoutSize Cutoutsize N/A deg N/A
cutoutSize Cutoutsize N/A deg N/A
FORMAT Output format Requested format of the image data N/A N/A
hFORMAT Output format Requested format of the image data N/A N/A
hINTERSECT Intersection type Relation of image and specified Region of Interest. N/A N/A
hPOS Position ICRS Position, RA,DEC, or Simbad object (e.g., 234.234,-32.45) deg pos.eq
hSIZE Field size Size in decimal degrees (e.g., 0.2 or 1,0.1) deg N/A
INTERSECT Intersection type Relation of image and specified Region of Interest. N/A N/A
POS Position ICRS Position, RA,DEC decimal degrees (e.g., 234.234,-32.46) deg pos.eq
SIZE Field size Size in decimal degrees (e.g., 0.2 or 1,0.1) deg N/A

Default Output Fields

The following fields are contained in the output by default. More fields may be available for selection; these would be given below in the VOTable output fields.

NameTable Head DescriptionUnitUCD
accref Product key Access key for the data N/A N/A
accsize File size Size of the data in bytes byte VOX:Image_FileSize
bandpassHi Band upper Upper limit of the bandpass (in BandPass_Unit units) m VOX:BandPass_HiLimit
bandpassId Bandpass Freeform name of the bandpass used N/A VOX:BandPass_ID
bandpassLo Band lower Lower limit of the bandpass (in BandPass_Unit units) m VOX:BandPass_LoLimit
bandpassRefval Band Ref. Characteristic quantity for the bandpass of the image m VOX:BandPass_RefValue
bandpassUnit Bandpass unit Unit of bandpass specifications (always m). N/A VOX:BandPass_Unit
centerAlpha Ctr. RA Approximate center of image, RA deg POS_EQ_RA_MAIN
centerDelta Ctr. Dec Approximate center of image, Dec deg POS_EQ_DEC_MAIN
coverage Coverage Field covered by the image deg N/A
dateObs Obs. date Epoch at midpoint of observation d VOX:Image_MJDateObs
embargo Embargo ends Date the data will become/became public a N/A
fieldBandKey Field/Band CARS field designation plus band N/A meta.id
fieldKey Field CARS field designation N/A meta.id
imageTitle Title Synthetic name of the image N/A VOX:Image_Title
instId Instrument Identifier of the originating instrument N/A INST_ID
magzp Mag. ZP AB Magnitude Zeropoint mag phot.mag;arith.zp
magzperr Err. Mag. ZP Estimated Magnitude Zeropoint Error mag stat.error;phot.mag;arith.zp
mime Type MIME type of the file served N/A N/A
nAxes #axes Number of axes in data N/A VOX:Image_Naxes
ncombine Combined Number of individual frames in this stack N/A meta.number
owner Owner Owner of the data N/A N/A
pixelScale Scales The pixel scale on each image axis deg/pix VOX:Image_Scale
pixelSize Axes Lengths Number of pixels along each of the axes pix VOX:Image_Naxis
pixflags P. Flags Flags specifying the processing done (C-original; F-resampled; Z-fluxes valid; X-not resampled; V-for display only N/A VOX:Image_PixFlags
refFrame Ref. Frame Coordinate system reference frame N/A VOX:STC_CoordRefFrame
seeing Seeing Measured image seeing arcsec instr.obsty.seeing
seeingerr Err. Seeing Measured image Seeing error arcsec stat.error;instr.obsty.seeing
texptime Tot. Exposure Total Exposure Time s time.duration;obs.exposure
wcs_cdmatrix CD matrix FITS WCS CDij matrix deg/pix VOX:WCS_CDMatrix
wcs_equinox Equinox Equinox of the given coordinates yr VOX:STC_CoordEquinox
wcs_projection Proj. FITS WCS projection type N/A VOX:WCS_CoordProjection
wcs_refPixel Ref. pixel WCS reference pixel pix VOX:WCS_CoordRefPixel
wcs_refValues Ref. values World coordinates at WCS reference pixel deg VOX:WCS_CoordRefValue

VOTable Output Fields

The following fields are available in VOTable output. The verbosity level is a number intended to represent the relative importance of the field on a scale of 1 to 30. The services take a VERB argument. A field is included in the output if their verbosity level is less or equal VERB*10.

NameTable Head DescriptionUnitUCD Verb. Level
centerAlpha Ctr. RA Approximate center of image, RA deg POS_EQ_RA_MAIN 0
centerDelta Ctr. Dec Approximate center of image, Dec deg POS_EQ_DEC_MAIN 0
imageTitle Title Synthetic name of the image N/A VOX:Image_Title 0
dateObs Obs. date Epoch at midpoint of observation d VOX:Image_MJDateObs 0
accref Product key Access key for the data N/A N/A 1
bandpassId Bandpass Freeform name of the bandpass used N/A VOX:BandPass_ID 10
accsize File size Size of the data in bytes byte VOX:Image_FileSize 11
pixelScale Scales The pixel scale on each image axis deg/pix VOX:Image_Scale 12
instId Instrument Identifier of the originating instrument N/A INST_ID 15
pixelSize Axes Lengths Number of pixels along each of the axes pix VOX:Image_Naxis 15
ncombine Combined Number of individual frames in this stack N/A meta.number 15
texptime Tot. Exposure Total Exposure Time s time.duration;obs.exposure 15
mime Type MIME type of the file served N/A N/A 20
nAxes #axes Number of axes in data N/A VOX:Image_Naxes 20
refFrame Ref. Frame Coordinate system reference frame N/A VOX:STC_CoordRefFrame 20
wcs_equinox Equinox Equinox of the given coordinates yr VOX:STC_CoordEquinox 20
wcs_projection Proj. FITS WCS projection type N/A VOX:WCS_CoordProjection 20
wcs_refPixel Ref. pixel WCS reference pixel pix VOX:WCS_CoordRefPixel 20
wcs_refValues Ref. values World coordinates at WCS reference pixel deg VOX:WCS_CoordRefValue 20
wcs_cdmatrix CD matrix FITS WCS CDij matrix deg/pix VOX:WCS_CDMatrix 20
bandpassUnit Bandpass unit Unit of bandpass specifications (always m). N/A VOX:BandPass_Unit 20
bandpassRefval Band Ref. Characteristic quantity for the bandpass of the image m VOX:BandPass_RefValue 20
bandpassHi Band upper Upper limit of the bandpass (in BandPass_Unit units) m VOX:BandPass_HiLimit 20
bandpassLo Band lower Lower limit of the bandpass (in BandPass_Unit units) m VOX:BandPass_LoLimit 20
pixflags P. Flags Flags specifying the processing done (C-original; F-resampled; Z-fluxes valid; X-not resampled; V-for display only N/A VOX:Image_PixFlags 20
coverage Coverage Field covered by the image deg N/A 20
fieldKey Field CARS field designation N/A meta.id 20
fieldBandKey Field/Band CARS field designation plus band N/A meta.id 20
magzperr Err. Mag. ZP Estimated Magnitude Zeropoint Error mag stat.error;phot.mag;arith.zp 20
seeing Seeing Measured image seeing arcsec instr.obsty.seeing 20
owner Owner Owner of the data N/A N/A 25
embargo Embargo ends Date the data will become/became public a N/A 25
magzp Mag. ZP AB Magnitude Zeropoint mag phot.mag;arith.zp 25
seeingerr Err. Seeing Measured image Seeing error arcsec stat.error;instr.obsty.seeing 25

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

VOResource XML (that's something exclusively for VO nerds)