PANORAMIC DEEP FIELDS -- HELP PAGE

The Panoramic Deep Fields

The Panoramic Deep Fields (PDF) are a deep multicolour survey of two 40 square degree fields. The imaging data for the survey was compiled by coadding SuperCOSMOS scans of UK Schmidt photographic plates. By using a median filter to subtract the background before coaddition, it was possible to use bad pixel rejection algorithms during the coaddition to produce deep clean images. As shown in Figure 1, the magnitude limits of coadded scans are significantly fainter than single plates and there is little contamination in the coadded data.

Figure 1 - Comparison of a single scan and a stack of 12 scans

Field centres, limiting magnitudes and the stellar FWHM of the images are summarised in Tables 1 and 2. Object catalogues were compiled with SExtractor and catalogues containing data for all 4 bands can be obtained in a SExtractor-style format. The completeness of the catalogues for stellar objects as a function of magnitude is plotted in Figure 2. Further information about the PDF can be found in Brown, Webster & Boyle (2000) and Brown, Webster & Boyle (2001).

Table 1 - Positions and Magnitude Limits

Field	Field Centre (J2000)	U	Bj	R	I
SGP	0:55:25 -27:46:45	22.0	23.5	22.0	20.0
F855	10:42:33 -0:15:44	22.0	23.5	22.5	20.0

Table 2 - Stellar FWHM

Field	U	Bj	R	I
SGP	2.9"	3.1"	2.9"	2.9"
F855	2.8"	3.0"	2.7"	2.7"

Figure 2 - Completeness as a function of magnitude

The PDF data release website provides acces to the PDF object catalogues and image data. The object catalogues are available in either text or html table format with a choice of 3 different sets of parameters (normal, short and long). Short provides RA, DEC (J2000) and calibrated SExtractor "Auto" magnitudes. Normal provides the same parameters as short along with SExtractor object classifications and photometric redshifts and the long format provides all 46 object parameters. Details on how SExtractor image parameters are determined is provided by Bertin & Arnouts (1996). 10 arcminute wide FITS images of objects can be obtained by clicking on the appropriate band in the far right hand column. The FITS header information includes a WCS and zero-point information.

Search Parameters

Co-ordinates

The co-ordinates are entered as RA, Dec in the J2000.0 system. The way in which they are entered is somewhat flexible. A full specification of RA & DEC ("hh hm hs dd dm ds") can be entered without using a comma to separate the two factors. If a partial specification is given, (ie. "hh, dd" or "hh hm, dd dm ds" etc.) components must be separated with a comma. Individual RA/DEC components can be separated by spaces or colons. eg.

"00:55:18.0 -26:25:30.0"

"0 55,-26 25 30"

"1, -26"
NOTE: (RA and DEC each have three "components" ie."hh hm hs" and "dd dm ds").
NOTE: (RA must be given in hours).

Radius

The search radius (given in arcseconds) specifies the radius within which to search for observations. The default value is 10 arcseconds with an enforced maximum 3600 arcsec and minimum of 0.01 arcsec. The "Submit query" button must then be clicked to receive a list of observations within the specified radius.

Max no. records

Maximum number of objects returned by the query form. This can not be greater than 1000.

Catalogue

Selects which catalogue is searched.

Mode

Selects how many parameters and in which format the catalogue data are provided in.

Table of Results

This is only intended as a brief summary of the results returned by the query form. For additional information about how image parameters are determined, please read Brown, Webster & Boyle (2000) and/or Bertin & Arnouts (1996).

Distance

The distance in arcseconds of the object from the given co-ordinate.

RA,Dec (ALPHA_J2000, DELTA_J2000)

The position of the object in J2000.0 co-ordinates.

X_IMAGE, Y_IMAGE

Pixel position of the object on the coadded scans.

MAG_AUTO

Adaptive aperture magnitudes similar to Kron magnitudes. Faint objects galaxies have been calibrated assuming that they are in the linear regime of the plate response while stellar magnitudes have been calibrated by fitting a polynomial to the relation between PDF instrumental magnitudes and calibrated CCD magnitudes.

MAG_ISO

Isophotoal magnitudes.

MAG_ISOCOR

Corrected isophotoal magnitudes.

MAG_BEST

SExtractor's best estimate of the magnitude from MAG_AUTO and MAG_ISO.

PEAK_MAG

Estimated peak surface brightness in magnitude per square arcsecond. The estimate of the peak surface brightness is only valid for the linear regime of the plate response.

ISOAREA_IMAGE

Isophotal area of object above analysis threshold in pixels.

ELLIPTICITY

Ellipticity of object (1-B/A).

THETA_J2000

Position angle (east of north).

CLASS_STAR

Output of SExtractor star-galaxy classifier. For saturated objects, the classifier breaks down and objects have been reclassified using peak intensity, area and instrumental magnitude. For Brown, Webster & Boyle (2001), objects were classified as stellar if CLASS_STAR was more than 0.7 in 3 bands, more than 0.75 in 2 bands or more than 0.85 in a single band.

E(B-V)

Dust extinction estimate from Schlegel et al.(1998) dust maps.

VIGNETTING

Estimated vignetting in magnitudes.

PHOTOZ

Photometric redshifts estimated with the polynomial fitting technique of Connolly et al.(1995). Photometric redshifts have been estimated for all objects with Bj and R photometry, this includes objects which are classified as stellar as a small fraction of "stellar" objects will be misclassified galaxies.

PHOTOZ_ERR

Estimated rms errors for the photometric redshifts. These have been estimated by measuring the rms of the difference between the photometric and spectroscopic redshifts as a function of Bj-R colour and photometric redshift.