Service Notice
Subject: CADC/CANFAR authentication downtime — Saturday, Sept 13 (12:00–8:00 pm PT)
Essential network maintenance in Victoria will take place on Saturday, Sept 13, from 12:00–8:00 pm Pacific Time. During this window, any CADC/CANFAR service that requires authentication will be unavailable (e.g., logins to portals, token issuance, authenticated APIs/Python Client/CLI jobs). Please plan accordingly and avoid starting jobs that need credentials during the outage. Other service access may also be affected. Thank you for your patience.
Data Description
Naming Convention
The names are of two sorts. The first sort starts with "G" (for "group") followed by a generation number (which is incremented every six months), followed by numbers indicating the RA and Dec of the group centre. For example: G002.003.844+33.133 is and older group centred on RA=33.133 and Dec=3.844. The other sort is based on survey from which the came, either the CFHTLS (with names like D3, W4 etc.) or the NGVS (NGVS+1+1 for example).
The group names are followed by a character(s) indicating the filter UGRIZ. The i.MP9702 filter is denoted "I2".
Images
These are simple FITS files (not multi-extension FITS files) measuring about 20000 pixels by 20000 pixels or about 1 degree by 1 degree, depending on the input dither pattern, and are about 1.7 Gb in size. They have a sky level of 0 counts. They are scaled to have a photometric zero-point of 30.000 in AB magnitudes. That is to say, for each source:
AB_magnitude = -2.5 * log10(ADU) + 30.000
The conversions to Vega and SDSS magnitudes can be found on the filter page.
Weight images
These are delivered with in a compressed format. To uncompress them, use CFITSIO's imcopy. For example:
imcopy G002.003.844+33.133.G.weight.fits.fz G002.003.844+33.133.G.weight.fits
The values of a weight map pixel is proportional to the inverse of the variance of that pixel in the main image.
Catalogues
All magnitudes are on the AB system. The catalogues have a header describing the columns:
# 1 NUMBER Running object number # 2 X_IMAGE Object position along x [pixel] # 3 Y_IMAGE Object position along y [pixel] # 4 ALPHA_J2000 Right ascension of barycenter (J2000) [deg] # 5 DELTA_J2000 Declination of barycenter (J2000) [deg] # 6 MAG_AUTO Kron-like elliptical aperture magnitude [mag] # 7 MAGERR_AUTO RMS error for AUTO magnitude [mag] # 8 MAG_BEST Best of MAG_AUTO and MAG_ISOCOR [mag] # 9 MAGERR_BEST RMS error for MAG_BEST [mag] # 10 MAG_APER Fixed aperture magnitude vector [mag] # 11 MAGERR_APER RMS error vector for fixed aperture mag. [mag] # 12 A_WORLD Profile RMS along major axis (world units) [deg] # 13 ERRA_WORLD World RMS position error along major axis [pixel] # 14 B_WORLD Profile RMS along minor axis (world units) [deg] # 15 ERRB_WORLD World RMS position error along minor axis [pixel] # 16 THETA_J2000 Position angle (east of north) (J2000) [deg] # 17 ERRTHETA_J2000 J2000 error ellipse pos. angle (east of north) [deg] # 18 ISOAREA_IMAGE Isophotal area above Analysis threshold [pixel**2] # 19 MU_MAX Peak surface brightness above background [mag * arcsec**(-2)] # 20 FLUX_RADIUS Fraction-of-light radii [pixel] # 21 FLAGS Extraction flags
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