Table of Agreed Catalog Parameters




1 Sequence number Running number for ease of reference, in strict order of image detections.
2 Isophotal flux Standard definition of summed flux within detection isophote, except that a detection filter is used to define pixel connectivity and hence which pixels to include. This helps to reduce edge effects for all isophotally derived parameters.
3 X coord Intensity-weighted isophotal centre-of-gravity in X.
4 Error in X Estimate of centroid error.
5 Y coord Intensity-weighted isophotal centre-of-gravity in Y.
6 Error in Y Estimate of centroid error.
7 Gaussian sigma These are derived from the three general intensity-weighted second moments. The equivalence between them and a generalised elliptical Gaussian distribution is used to derive:
Gaussian sigma = (sigma(a)2+ sigma(b)2)1/2
ellipticity = 1.0-sigma(a)/sigma(b)
position angle = angle of ellipse major axis w.r.t X axis.
8 Ellipticity
9 Position angle
10 Areal profile 1 Number of pixels above a series of levels relative to local sky. The levels are set at T, 2T, 4T, 8T ... 128T, where T is the threshold. These can be thought of as a sort of poor man's radial profile. Note that for now, for deblended (i.e. overlapping) images, only the first areal profile is computed and the rest are set to -1, flagging the difficulty of computing accurate profiles.
11 Areal profile 2
12 Areal profile 3
13 Areal profile 4
14 Areal profile 5
15 Areal profile 6
16 Areal profile 7
17 Areal profile 8
18 Peak height In counts relative to local value of sky - also zeroth order aperture flux.
19 Error in pk ht
20 Aperture flux 1 To be used if a single number is required to represent the flux for ALL objects. Basically aperture integration within core radius rc (in the FITS header), but modified to fit 'cores' simultaneously in case of overlapping images. Best selected using ~<FWHM> for site+instrument. Combined with later-derived aperture corrections for general photometry.
21 Error in flux
22 Aperture flux 2 A series of different aperture measures similar to parameter 20. Together with parameter 18 these give a simple curve-of-growth analysis. The set of 13 aperture radii are: 1/2×rc, 1/sqrt2×rc, rc, sqrt2×rc, 2×rc, 2sqrt2×rc, 4×rc, 4sqrt2×rc, 8×rc, 8sqrt2×rc, 16×rc, 16sqrt2×rc, 32×rc. The radius 4×rc ensures ~99% of PSF flux. Extras for generalised galaxy photometry further spaced by sqrt2 in radius to ensure correct sampling out to reasonable range of aperture sizes. Largest would be 32×rc i.e. ~30arcsec diameter. Note these are all corrected for pixels from overlapping neighbouring images.
23 Error in flux
24 Aperture flux 3
25 Error in flux
26 Aperture flux 4
27 Error in flux
28 Aperture flux 5
29 Error in flux
30 Aperture flux 6
31 Error in flux
32 Aperture flux 7
33 Error in flux
34 Aperture flux 8
35 Error in flux
36 Aperture flux 9
37 Error in flux
38 Aperture flux 10
39 Error in flux
40 Aperture flux 11
41 Error in flux
42 Aperture flux 12
43 Error in flux
44 Aperture flux 13
45 Error in flux
46 Petrosian radius rp as defined in Strauss et al. (AJ, 124, 1810).
47 Kron radius rk as defined in Bertin and Arnouts A&A Supp. 117 393.
48 FWHM radius rfwhm average image radius at half peak height.
49 Petrosian flux Flux within circular aperture to k1 × rp
50 Error in flux
51 Kron flux Flux within circular aperture to k2 × rk
52 Error in flux
53 FWHM flux Flux within circular aperture to k3 × rfwhm - simple alternative.
54 Error in flux
55 Error bit flag Bit pattern listing various processing error flags.
56 Sky level Local interpolated sky level from background tracker.
57 Sky variance Local estimate of variation in sky level around image.
58 Child/parent Flag for parent or part of deblended deconstruct.

The following are accreted directly after standard catalog generation.

59 RA RA and Dec explicitly put in columns for overlay programs that cannot, in general, understand astrometric solution coefficients. Derived exactly from WCS in header and X, Y in parameters 3 & 5.
60 Dec
61 Class'n stat 1 Flag indicating probable classification: e.g. -1 stellar, +1 non-stellar, 0 noise.
62 Class'n stat 2 An equivalent N(0,1) measure of how stellar-like an image is, used in deriving parameter 61 in a 'necessary but not sufficient' sense.

From the further processing pipeline after deriving a suitable PSF.

63 PSF flux Fitted flux from PSF.
64 Error in flux
65 X coord Updated PSF-fitted X centroid.
66 Error in X coord
67 Y coord Updated PSF-fitted Y centroid.
68 Error in Y coord
69 PSF fit chi2 Standard normalised variance of fit.
70 ndf(PSF) No. of degrees of freedom for PSF fit.
71 1D Sersic flux Fitted flux for Sersic profile.
72 1D scale length Scale factor of fit.
73 1D power index Power law index of fit.
74 1D Sersic fit chi2 Standard normalised variance of fit.
75 ndf(S1) No. of degrees of freedom for 1D Sersic fit.
76 2D Sersic flux Fitted flux for PSF-deconvolved 2D Sersic fit.
77 2D scale length Scale factor of fit.
78 2D power index Power law index of fit.
79 2D Sersic fit chi2 Standard normalised variance of fit.
80 ndf(S2) No. of degrees of freedom for 1D Sersic fit.

For numerical stability the Sersic fits will use the previously derived x-y coordinates