CFTHTLenS CATALOGUE DATA DESCRIPTION ================================== Author: Hendrik Hildebrandt (email: hendrik@astro.uni-bonn.de) - v1.0: 2012-10-23 - v1.1: 2018-01-31 Fixed a typo in the description of the PZ_full column. In v1.0 of this README it said: "The first bin is centered at z=0.025." The corrected statement reads: "The first bin is centered at z=0.03." ACKNOWLEDGEMENT =============== Acknowledging the use of CFHTLenS data products in publications: The use of the CFHTLenS imaging, photometry or shear catalogues should be acknowledged in publications by including the paragraph listed below, in addition to citing specific CFHTLenS articles within the text. For publications that use the shear and photometric catalogues we provide an example paragraph that includes all the relevant references: "We use data from the Canada-France-Hawaii Lensing Survey (Heymans et al. 2012), hereafter referred to as CFHTLenS. The CFHTLenS survey analysis combined weak lensing data processing with THELI (Erben et al. 2012), shear measurement with lensfit (Miller et al. 2012), and photometric redshift measurement with PSF-matched photometry (Hildebrandt et al. 2012). A full systematic error analysis of the shear measurements in combination with the photometric redshifts is presented in Heymans et al. (2012), with additional error analyses of the photometric redshift measurements presented in Benjamin et al. (2012)." For publications which use the imaging data alone, cite Erben et al. (2012). For publications which use the photometry alone, cite Erben et al. (2012) and Hildebrandt et al. (2012). Please also include the following paragraph in your acknowledgements section: "This work is based on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council (NRC) of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique (CNRS) of France, and the University of Hawaii. This research used the facilities of the Canadian Astronomy Data Centre operated by the National Research Council of Canada with the support of the Canadian Space Agency. CFHTLenS data processing was made possible thanks to significant computing support from the NSERC Research Tools and Instruments grant program." We are very keen for the community to make full use this data product, so do not hesitate to contact the CFHTLenS PIs, Ludovic Van Waerbeke (waerbeke[-at-]phas.ubc.ca) and Catherine Heymans (heymans[-at-]roe.ac.uk) if you have any questions about the survey and the catalogues. CATALOGUE CREATION ================== Summary of the catalogue creation: The catalogues were created from the CFHTLenS images released at PLEASE INSERT WEBSITE FOR IMAGES HERE The following steps were performed for the photometric analysis. Details can be found in Hildebrandt et al. (2012) 1. Manual star selection from a high-threshold, single-band SExtractor catalogue. 2. After selecting stars from the detection image (i- or y-band, with the former being the old i-band filter and the latter being the new i-band filter) these star catalogues are used to Gaussianise the images. 3. Then SExtractor is run in dual image mode six times. The detection image is the unconvolved i-/y-band image and the measurement images are the Gaussianised images in the five bands and - in the sixth run - the unconvolved i-/y-band image. The last run is performed to get total magnitudes in one band, whereas the first five runs yield accurate colours based on isophotal magnitudes. All magnitudes are in the AB system. 4. Limiting magnitudes are added for each object based on SExtractor RMS check images. 5. Extinction values are added based on the Schlegel maps (Schlegel et al. 1998). 6. The total magnitude in the i/y band are combined with the colour estimates, the limiting magnitudes (to decide whether an object is detected in a given band), and the extinction values to yield estimates of the total magnitudes in the other bands (MAG_[ugriyz]). IMPORTANT: This assumes that there are no colour gradients in the objects. For galaxies with colour gradients the magnitudes in the ugrz-bands might be biased and only the i/y-band magnitudes are reliable. Note that the isophotal magnitudes do not appear in the released catalogues anymore. MAG_[ugriyz] are the only magnitude estimates and can be used to calculate accurate colours as well. 7. A mask column based on the final, eye-balled and modified masks is added. 8. BPZ is run to get the photo-z's. 9. Absolute rest-frame magnitudes in the MEGACAM filters as well as stellar masses (see Velander et al. 2012 for details) are added based on the BPZ photo-z estimate and a best-fit template from the Bruzual & Charlot (2003) library. This step is performed keeping the redshift fixed using the LePhare (Arnouts et al. 2002) code and the Ilbert et al. (2010) technique. Shear measurement was made as described by Miller et al (2012) and Heymans et al. (2012), to which reference should be made before using the shear measurements. All calibrated, individual exposures were passed to the shear measurement stage, which comprised joint fitting of models to individual galaxies, taking into account the varying PSF on each individual exposure. Corrections to resulting shear estimates should be made following Miller et al. (2012) and Heymans et al. (2012). COLUMN DESCRIPTION ================== All quantities in the catalogue refer to the detection band if not otherwise specified, either by an _[ugriyz] or in obvious cases (photo-z, stellar mass, etc.). Additional information on certain columns in the catalogue: - field: Field identifier composed of the region (first two characters), the relative position in R.A. with respect to the centre of this region (3rd&4th character; "m" indicates minus, i.e. lower R.A. than the centre and "p" indicates plus, i.e. larger R.A. than the centre), and the relative position in Dec with respect to the centre of this region (3rd&4th character; "m" indicates minus, i.e. lower Dec than the centre and "p" indicates plus, i.e. larger Dec than the centre), - MASK: If MASK>0 the object lies within a mask. However, objects with MASK<=1 can safely be used for most scientific purposes. - T_B: BPZ spectral type. 1=CWW-Ell, 2=CWW-Sbc, 3=CWW-Scd, 4=CWW-Im, 5=KIN-SB3, 6=KIN-SB2. Note that we use a recalibrated template set described in Capak et al. (2004) and that the templates are interpolated, hence fractional types occur. - NBPZ_FILT, NBPZ_FLAGFILT, NBPZ_NONDETFILT: The number of filters in which an object has 'reliable photometry' (NBPZ_FILT, magnitude errors < 1 mag and object brighter than the limiting magnitude); number of filters in which an object has formal magnitude errors of 1 mag or larger (NBPZ_FLAGFILT); number of filters in which an object is fainter than the formal limiting magnitude (NBPZ_NONDETFILT). If an object would fall into FLAGFILT AND NONDETFILT it is listed under FLAGFILT! Magnitude errors refer to MAG_ISO. - BPZ_FILT, BPZ_FLAGFILT, BPZ_NONDETFILT: These keys contain a 'binary' encoding which filters fulfil the respective conditions. Filter u* is assigned a '1', "g'" = '2', "r'" = '4', "i'" = '8' and "z'" = '16'. The keys BPZ_FILT etc. represent the sums of the filters fulfilling the corresponding criteria. - PZ_full: This is the full P(z) to z=3.5. There are 70 columns sampling P(z) at intervals of dz=0.05. The first bin is centered at z=0.03. Note these 70 columns do not always sum to 1. There is a final bin not included in the catalogues with z>3.5 that, in a small number of cases, has non-zero probability. In CFHTLenS analysis we set a hard prior that there is zero probability past z>3.5, which corresponds to normalising each P(z) to one. For future flexibility however we do not impose this normalisation on the catalogue, leaving it to the user to apply. - star_flag: Stars and galaxies are separated using a combination of size, i/y-band magnitude and colour information. For i<21, all objects with size smaller than the PSF are classified as stars. For i>23, all objects are classified as galaxies. In the range 21-exp: the lensfit PSF model ellipticity components 1,2 (top-hat weighted as above) on each exposure i. FIELD SELECTION =============== As described in Heymans et al (2012) some MEGACAM fields do not pass the lensing residual systematics tests. For any study that uses a shear two-point correlation function, only the fields that pass the systematics tests of Heymans et al 2012 can be used. For other studies, such as galaxy-galaxy lensing or cluster studies we recommend that the measurement is made and compared for the full data set and the 75% of the data which passes the field selection. Good fields list: ---------------- W1m0m0_i W1m0m3_i W1m0m4_y W1m0p1_i W1m0p2_i W1m0p3_i W1m1m0_i W1m1m2_i W1m1m3_i W1m1m4_y W1m1p3_i W1m2m1_i W1m2m2_i W1m2m3_i W1m2p1_i W1m2p2_i W1m3m0_i W1m3m2_i W1m3m4_y W1m3p1_i W1m3p3_i W1m4m0_i W1m4m1_i W1m4m3_i W1m4m4_y W1m4p1_i W1p1m1_i W1p1m2_i W1p1m3_i W1p1m4_y W1p1p1_y W1p1p2_i W1p1p3_i W1p2m0_i W1p2m2_i W1p2m3_i W1p2m4_y W1p2p1_i W1p2p2_i W1p2p3_i W1p3m1_i W1p3m2_i W1p3m3_i W1p3m4_y W1p3p1_y W1p3p2_i W1p3p3_i W1p4m0_i W1p4m1_i W1p4m2_i W1p4m3_i W1p4m4_y W1p4p1_i W1p4p2_i W1p4p3_i W2m0m0_i W2m0m1_i W2m0p1_i W2m0p2_i W2m1m0_i W2m1m1_i W2m1p1_i W2m1p3_i W2p1m0_i W2p1p1_i W2p1p2_i W2p2m0_i W2p2m1_i W2p2p1_i W2p2p2_i W2p3m0_i W2p3m1_i W2p3p1_i W2p3p3_i W3m0m1_y W3m0m2_i W3m0m3_i W3m0p2_i W3m0p3_i W3m1m0_i W3m1m2_i W3m1m3_i W3m1p1_i W3m1p2_i W3m1p3_i W3m2m1_y W3m2m2_i W3m2m3_i W3m2p1_y W3m2p2_i W3m3m0_i W3m3m1_i W3m3m2_i W3m3m3_i W3m3p1_i W3m3p2_i W3p1m0_i W3p1m1_i W3p1m2_i W3p1m3_i W3p1p2_i W3p1p3_i W3p2m0_i W3p2m3_y W3p2p3_i W3p3m1_i W3p3m3_i W3p3p1_i W3p3p2_i W3p3p3_i W4m0m2_i W4m0p1_i W4m1m0_i W4m1m1_i W4m1m2_i W4m1p1_y W4m2m0_i W4m2p1_i W4m2p3_y W4m3m0_i W4m3p1_i W4m3p2_i W4m3p3_y W4p1m0_i W4p1m1_i W4p1m2_i W4p2m0_i W4p2m1_i W4p2m2_i Bad fields list: --------------- W1m0m1_i W1m0m2_i W1m1m1_i W1m1p1_i W1m1p2_i W1m2m0_i W1m2m4_y W1m2p3_i W1m3m1_i W1m3m3_i W1m3p2_i W1m4m2_i W1m4p2_i W1m4p3_i W1p1m0_i W1p1p1_i W1p2m1_i W1p2p2_y W1p3m0_i W1p3p1_i W1p4p2_y W2m0p3_i W2m1p2_i W2p1m1_i W2p1p1_y W2p1p3_i W2p2p2_y W2p2p3_i W2p3p2_i W3m0m0_i W3m0m1_i W3m0p1_i W3m1m1_i W3m1p3_y W3m2m0_i W3m2m1_i W3m2p1_i W3m2p3_i W3m2p3_y W3m3p1_y W3m3p3_i W3p1p1_i W3p2m1_i W3p2m2_i W3p2m3_i W3p2p1_i W3p2p2_i W3p3m0_i W3p3m1_y W3p3m2_i W3p3m2_y W3p3p2_y W4m0m0_i W4m0m1_i W4m1m1_y W4m1p1_i W4m1p2_y W4m1p3_y W4m2p2_y W4p1p1_i