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Imaging Data Products


Image Parameters

The results of the imaging pipelines (described below in § 4.4) are summarized in Table 6, and the apertures used for radial profile measurements are in Table 7. For each object, we measure the position, several varieties of the flux, morphological parameters, and a provisional classification. We also include informational flags on each pixel in the images (Table 8) and each object (Table 9) and summary flags and statistics for each field (Table 16). The choice of flags and which measure of flux and shape to use are dictated by the science goals of the SDSS. The catalog contains over 120 parameters and flags measured for 13,804,448 objects. 10,947,783 of these are unique, well-measured astrophysical objects.

The SDSS object catalogs are matched against the FIRST becker95, ROSAT voges99, and USNOA2.0 monet databases; the resulting parameters are described in Table 10.


Each corrected frame is a FITS image for one filter, 2048 columns tex2html_wrap_inline2843 1489 rows, with row number increasing in the scan direction. These are the imaging frames with flat field, bias, cosmic ray, and pixel defect corrections applied. A raw image contains 1361 rows, and a corrected frame has the first 128 rows of the following corrected frame appended to it. The pixels subtend 0.396'' square on the sky.

Header information using the World Coordinate System (WCS) calabretta01 allows standard astronomical FITS tools to convert pixel position to tex2html_wrap_inline2847 (§ 4.2.2).

Binned Images

Each file is a FITS image for one filter, tex2html_wrap_inline2849 pixels, with WCS information. These are the corrected frames with detected objects removed and binned tex2html_wrap_inline2839 pixels.

Mask Frame

Each file is a binary FITS table for one filter. Each row of the table describes a set of pixels in the corrected frame, using mask values described in Table 8.

Atlas Image

For each detected object, the atlas image comprises the pixels in a rectangular area associated with the object in each filter. These are provided through a database, as either a JPEG color image, or as a FITS file for each selected filter.

Color Image

We combine the corrected frames from the tex2html_wrap_inline2853 and i filters and produce a color image with the filters corresponding to blue, green, and red, respectively. The intensity mapping of each color is adjusted to enhance the appearance of these images. We use the same mapping for all of the color images.

next up previous
Next: Spectroscopic Data Products Up: Data Products Previous: ParametersClasses, and Associations

Michael Strauss
Thu Jan 30 11:15:34 EST 2003