Terapix T0005 pagesImportant :
|
1. T0005 quick summary table : Exposure time, Seeing, Effective area, Star/Disk Completeness |
2. T0005 Synoptic Table : explanatory table |
3. T0005 astrometric and photometric calibration |
4. T0005 CFHTLS / SDSS comparisons |
5. T0005 file naming convention |
6. T0005 catalogue parameters |
7. The CFHTLS Data Access Policy |
9. Acknowledgement |
Improvements compared to T0004
All flat-fields have been re-generated at CFHT. This means that all weight-maps have been recreated. Also CFHT have recomputed the photometric calibrations for all data (new PHOT_C values in all headers).
Deep stacks have longer integration times
Significant increase in coverage in five filter area for the wide fields.
CFHTLS T0005 target lists:
Deep fields with 25% best seeing images: D1-25, D2-25, D3-25 and D4-25 Deep fields with 85% best seeing images: D1-85, D2-85, D3-85 and D4-85 Wide fields: W1, W2, W3 and W4
Positions of Deep and Wide fields in the sky.
Image selection criteria for the stacking process: Data obtained between: May 26, 2003 and February 16, 2008. Terapix Class : A or B Exp. time: > 60 sec. Seeing : < 1.3" , except for u* (<1.4") Airmass: < 1.7 Skyprobe value: <2.0 Mag. (security limit)
Overview of T0005 stacks and status of the CFHTLS-T0005 sky coverage
Number of Deep stacks: 48 (24 D25+24 D85: filter i.9701 (i.2003) and i.9702 (i.2007) not staked together) Number of Wide stacks: 804 (129 u, 176 g, 178 r, 173 i, 148 z) Filter distribution of wides:
| Wide field | gri only | griz only | all ugriz | all gri (=chi2) | Total u/g/r/i/ or z |
| W1 | 23 | 0 | 49 | 72 | 72 |
| W2 | 5 | 0 | 25 | 30 | 30 |
| W3 | 0 | 19 | 30 | 49 | 49 |
| W4 | 0 | 0 | 20 | 25 | 25 |
| Total | 28 | 19 | 124 | 176 | 176 |
| W1-ugriz | W2-ugriz | W3-ugriz | W4-ugriz |
| Quick T0005 stack summary table and printable table | The Synopic T0005 Table |
Overview photometry:
Magnitudes: AB Megacam instrumental system Magnitude zero points : The zero points of all images are set to 30 AB magnitudes. The images have an effective exposure time of one second. SDSS/CFHTLS transformations resulting from the SNLS group (Regnault et al. ):
. uCFHTLS - uSDSS = -0.214 * (u-g)SDSS
. gCFHTLS - gSDSS = -0.156 * (g-r)SDSS
. rCFHTLS - rSDSS = -0.000 * (g-r)SDSS
. iCFHTLS - iSDSS = -0.094 * (r-i)SDSS for the i.9701 filter
. iCFHTLS - iSDSS = -0.003 * (r-i)SDSS for the i.9702 filter
. zCFHTLS - zSDSS = +0.050 * (i-z)SDSS
Mean rms external errors with respect to SDSS (when available): 0.02 mag. , but depends on the field and the filter.
Fields in common between T0004 and T0005 have the same magnitude zero points as demonstrated from the stellar color-color plots and past SDSS comparisons.
WARNING: there are several fields with an offset in u*-band of around 0.1 magnitudes.
A detailed CFHTLS/SDSS comparison.
Overview of astrometric solutions
Calibration catalogue: 2MASS. For each patch (D1, D2, D3, D4, W1, W2, W3, W4), all CFHTLS images located in the field with exp. time >180s. , airmass <1.7 and seeing<1.5" have been used to set the astrometric calibration of each field used later for the stacks.
Mean rms external error with respect to 2MASS: 0.24"+/-0.02" in both directions (instead of 0.42" in previous releases using USNO-B, with significant anisotropy)).
Mean rms internal error is 0.017"+/-0.002" in both directions (instead of 0.035" before).
Mean systematic offset of stacks with respect to 2MASS astrometric positions: 0.017"
More detailed information can be found here
Catalogue parameters
All fields having at least rgi image stacks have an associated chi2 images and catalogues centered on the i-band stack. Otherwise, simple single-band ldac catalogues are delivered. The catalogues contain the following Sextractor parameters.
Catalogue parameters and filenames are described in data and parameter description, except for the 'merged ugriz' that contain less information (see the item 'merged catalogue' in the T0005 explanatory table).
Data products and filenames
Terapix products relating to T0005 stacks available at CADC to CFHTLS registered users are:
| Data | File Name | Type | Nb Files |
| Wide stacks | CFHTLS_W_filter_RA-DEC_T0005.fits | FITS image | 806 |
| Wide weights | CFHTLS_W_filter_RA-DEC_T0005_weight.fits | FITS image | 806 |
| Wide chi2 | CFHTLS_W_gri_RA-DEC_T0005.fits | FITS image (only stacks with at least gri) | 176 |
| Wide chi2 weight | CFHTLS_W_gri_RA-DEC_T0005_weight.fits | FITS image (only stacks with at least gri) | 176 |
| Wide masks | CFHTLS_W_RA-DEC_T0005.reg | ASCII DS9 compliant in WCS | 198 |
| Wide chi2 catalogue | CFHTLS_W_filter_RA-DEC_T0005.cat | ASCII table (only stacks with at least gri) | 800 |
| Wide individual catalogue | CFHTLS_W_filter_RA-DEC_T0005.ldac | LDAC FITS table | 804 |
| Wide merged ugriz catalogue | CFHTLS_W_ugriz_RA-DEC_T0005.cat | ASCII table (only stacks with at least gri) | 171 |
| Deep stacks 25% | CFHTLS_D-25_filter_RA-DEC_T0005.fits | FITS image | 24 |
| Deep weight 25% | CFHTLS_D-25_filter_RA-DEC_T0005_weight.fits | FITS image | 24 |
| Deep chi2 25% | CFHTLS_D-25_gri_RA-DEC_T0005.fits | FITS image | 4 |
| Deep chi2 weight 25% | CFHTLS_D-25_gri_RA-DEC_T0005_weight.fits | FITS image | 4 |
| Deep masks 25% | CFHTLS_D_RA-DEC_T0005.reg | ASCII DS9 compliant in WCS | 4 |
| Deep 25% chi2 catalogue | CFHTLS_D-25_filter_RA-DEC_T0005.cat | ASCII table | 24 |
| Deep 25% individual catalogue | CFHTLS_D-25_filter_RA-DEC_T0005.ldac | LDAC FITS table | 24 |
| Deep 25% merged ugriz catalogue | CFHTLS_D-25_ugriz_RA-DEC_T0005.cat | ASCII table | 4 |
| Deep stacks 85% | CFHTLS_D-85_filter_RA-DEC_T0005.fits | FITS image | 24 |
| Deep weight 85% | CFHTLS_D-85_filter_RA-DEC_T0005_weight.fits | FITS image | 24 |
| Deep chi2 85% | CFHTLS_D-85_gri_RA-DEC_T0005.fits | FITS image | 4 |
| Deep chi2 weight 85% | CFHTLS_D-85_gri_RA-DEC_T0005_weight.fits | FITS image | 4 |
| Deep masks 85% | CFHTLS_D_RA-DEC-T0005.reg | ASCII DS9 compliant in WCS | 4 (same as D-25) |
| Deep 85% chi2 catalogue | CFHTLS_D-85_filter_RA-DEC_T0005.cat | ASCII table | 24 |
| Deep 85% individual catalogue | CFHTLS_D-85_filter_RA-DEC_T0005.ldac | LDAC FITS table | 24 |
| Deep 85% merged ugriz catalogue | CFHTLS_D-85_ugriz_RA-DEC_T0005.cat | ASCII table | 4 |
Individual weight map images have been generated for each CFHT FITS image, their QFITs-in, as well as the QFITS-out quality assessment outputs of each stack are available at CADC.
Important note about the catalogues at CADC
Catalogues with names like 'CFHTLS_D*/W*_z_RA-DEC_T0005.cat' are chisquared catalogues. They are only produced when at least the g,r and i data are available. All catalogues of the kind 'CFHTLS_D*/W*_u,g,r,i,z_RA-DEC_T0005.cat' are extracted with the same chisquared detection image and contain the same objects (i.e., they are all aperture-matched). Columns of catalogs with '.cat' and 'ldac' extentions are defined in the '.param' files. They are listed in the CFHTLS catalogue parameter list. The '.cat' file contains also the E(b-v) in the last column.
Access to T0005 release products (restricted to CFHTLS users):
Reminder: CADC is the ONLY access point to CFHTLS release. Please read the data access policy as defined by the CFHT Board of Directors.
The deep and wide T0005 release at CADC (link not active yet).
Annex:
Overview of CFHTLS Data Products.
