SuperCOSMOS Sky Surveys

SHS Homepage

Introduction

Get an IMAGE

Get a CATALOGUE

Sky coverage

Documentation

Release History

Other Wavebands

Related links

IFA ROE

Guide to object catalogue data from the SHS

Objects extracted by the web-form, Get a Catalogue, are described by a set of image parameters. These parameters are determined during the SuperCOSMOS Image Analysis mode (IAM) and primarily come from moments of the pixel distribution, up to second order together with results of image deblending. For a discussion of IAM go here (some of the parameters i.e. the COSMOS magnitude and parameters 31 & 32 have been re-defined since this document was written and have been replaced by a calibrated SuperCOSMOS magnitude, a N(0,1) profile classification statistic, and a SuperCOSMOS profile magnitude.

Updates to the on-line data and associated access software are listed in the Release History.

The extraction form can return a catalogue containing either the full parameters associated with the prime waveband selection or a useful subset which includes paired in parameters from the other associated surveys (matched SR and eventually first epoch SR and I). The subset selection (default) should satisfy most users requirements.

Description of subset parameters
Description of full parameters

For the complete beginner a short step-by-step guide for a typical IAM catalogue extraction from the SHS is given here.

The IAM catalogue listing can be returned as a FITS file, a tab seperated ascii file compatible with GAIA, or a plain ascii file.

NULL values
Null values occur in the FITS/ascii/tab-seperated tables where there is missing or un-matched data. The Null values for each parameter are as follows:
Image Areas: 0
Ellipticities: 9.999
Magnitudes: 99.999
Profile Statistic N(0,1): 999.99
Blend and Quality parameters: 99999

A secondary magnitude of 99.999 indicates one of the following:

the exposure in the seondary waveband does not exist or has not been measured, if this is the case all objects in this waveband will be entered as 99.999
the object is too faint or has a colour that prevents it from being detected on the secondary plate
pairing problems

Listings of the parameters returned by the "subset" and "full" options are given below.

Apart from the magnitudes, ellipticities, profile statistics, blend and quality flags available in the matched H-alpha/SR2 and placeholders (with Null values) for the first epoch SR1 and I data (that will be incorporated in due course) the remaining parameters (positions, epoch, position angle, image classification and field number) are derived from the measurement of the survey exposure in the primary waveband selected on the form.

Parameters returned if "subset" selected

Parameters returned if "all" selected

No. Name Type Description Units
1 RA Double Celestial Right Ascension radians (FITS), hms (ASCII) or degrees (tab)
2 DEC Double Celestial Declination radians (FITS), dms (ASCII) or degrees (tab)
3 EPOCH Real Epoch year
4 l2 Real Galactic longitude dec.degrees
5 b2 Real Galactic latitude dec.degrees
6 R_Ha Real H-alpha equivalent R-mag mags
7 SR2 Real matching SR magnitude (SR2) mags
8 SR1 Real First epoch SR magnitude (SR1) mags
9 I Real First epoch I magnitude mags
10 AREA_Ha Integer Total area H-alpha image pixels
11 AREA_SR2 Integer Total area SR2 image pixels
12 AREA_SR1 Integer Total area SR1 image pixels
13 AREA_I Integer Total area I image pixels
14 ELL_Ha Real H-alpha image ellipticity
15 ELL_SR2 Real SR2 image ellipticity
16 ELL_SR1 Real SR1 image ellipticity
17 ELL_I Real I image ellipticity
18 PRFSTT_Ha Real H-alpha N(0,1) profile classification statistic 0.001 sigma
19 PRFSTT_SR2 Real SR2 N(0,1) profile classification statistic 0.001 sigma
20 PRFSTT_SR1 Real SR1 N(0,1) profile classification statistic 0.001 sigma
21 PRFSTT_I Real I N(0,1) profile classification statistic 0.001 sigma
22 BLEND_Ha Integer H-alpha Deblending flag (0 if not deblended)
23 BLEND_SR2 Integer SR2 Deblending flag (0 if not deblended)
24 BLEND_SR1 Integer SR1 Deblending flag (0 if not deblended)
25 BLEND_I Integer I Deblending flag (0 if not deblended)
26 QUAL_Ha Integer H-alpha image Quality flag
27 QUAL_SR2 Integer SR2 image Quality flag
28 QUAL_SR1 Integer SR1 image Quality flag
29 QUAL_I Integer I image Quality flag
30 PA Integer Celestial position angle (selected band) degrees
31 CLASS Integer Classification flag (selected band)
32 FIELD Integer Schmidt H-alpha survey field number (4-degree centres)
33 XMIN Integer Left extent 0.01 microns
34 XMAX Integer Right extent 0.01 microns
35 YMIN Integer Bottom extent 0.01 microns
36 YMAX Integer Top extent 0.01 microns
37 IPEAK Integer Brightest intensity above sky
38 MAG Real COSMOS magnitude magnitudes
39 ISKY Integer Sky intensity at XCEN_I, YCEN_I
40 XCEN_I Integer Intensity weighted X centroid 0.01 microns
41 YCEN_I Integer Intensity weighted Y centroid 0.01 microns
42 A_U Integer Unweighted semi-major axis 0.01 microns
43 B_U Integer Unweighted semi-minor axis 0.01 microns
43 THETA_U Integer Unweighted orientation degrees
44 THETA_I Integer Weighted orientation degrees
45 AP(1) Integer Area above areal profile level 1 pixels
46 AP(2) Integer Area above areal profile level 2 pixels
47 AP(3) Integer Area above areal profile level 3 pixels
48 AP(4) Integer Area above areal profile level 4 pixels
49 AP(5) Integer Area above areal profile level 5 pixels
50 AP(6) Integer Area above areal profile level 6 pixels
51 AP(7) Integer Area above areal profile level 7 pixels
52 AP(8) Integer Area above areal profile level 8 pixels
53 PRFMAG Integer SuperCOSMOS profile magnitude millimags

WFAU, Institute for Astronomy,
Royal Observatory, Blackford Hill
Edinburgh, EH9 3HJ, UK

M.Read@roe.ac.uk
30/7/2008