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Data Products
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In the different data releases the following data products are made publicly available in different combinations. Imaging data is restricted to ESO member states for an one year period. Bulk data are only available upon request.
Note that the calibrated images being distributed have not been corrected for cosmetic defects. In particular, they contain bad columns, cosmic rays and the vignetted region at the top and bottom edges of the frames. However, all of these artifacts have been taken into account in the production of the object catalogs and the information available in them allows one to filter out affected objects.
To provide approximate astrometric information the CD-matrix convention, as given in the Users Guide for the Flexible Image Transport System 1997 version 4, has been adopted to describe the world-coordinate system, and included in the fits header of each frame. Even though this is in general a reasonable approximation it is not appropriate to account for the distortions of the frames. Therefore,when object catalogs are overlayed onto the images some residuals are visible, especially at the corners of the images.
The photometric zero-point for each frame after the absolute photometric calibration of the frame appears in the header of the image. A full description of the EIS specific keywords is also provided.
These sections are mapped using the conic equal area (COE) projection (Greisen & Calabretta 1996). Note that this projection is not handled by all display-tools but has already been implemented in the ESO SkyCat.
The available images are lossy compressed using a HCOMPRESS library originally written by White (1992) for the STScI. The coadded sections have been compressed using a very high compression scale of 200 (scale 20 in the case of WFI sections). In addition to the compression, the images are re-sampled by a factor of 0.5 in both directions using the re-sampling code developed by Devillard (1997), which is part of the eclipse library. To perform these conversions we have used a program written by Allan Brighton.
Of course the compression is well visible in the resulting images (see compression tests), but in direct comparison it is very hard to even find a single object suppressed in the compressed version.
These sections are handled by an on-line server, similar to that avaiable for the Digital Sky Survey. A preliminary object catalog, containing only position and shape information is also available on an on-line server. For the display of the sections and the catalog SkyCat can be used as an interface (you need to configure it properly to make the EIS catalogs available).
This image is meant to give a general overview of the whole patch and it has been produced by rebinning (3 arcsec pixel size) and coadding the sections. This is a standard output of the pipeline (~25 Mb).
The latter type of cutout you may also retrieve by entering the EIS cluster candidate name in the Object/Cluster Name field of the query form. By using this form you may specify different sizes of the cutout.
A preliminary list of EIS cluster candidates is presented in Olsen et al. 1999.
The name convention of the catalogs and single frame images are based on the EIS tiles A(i,j). Where i and j refer to row and column numbers of the observation, respectively. For a full description of the parameters available see the data release accompanying paper (Nonino et al. 1998).
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Last update: Feb 13, 2001 |