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4 Data products

The EIS pipeline produces a wide array of intermediate products, both images and catalogs, as well as a large set of logs, reports and diagnostics. A full description of these products is beyond the scope of the present paper and will be presented elsewhere.

In this preliminary release the following data are publicly available at "'':

Single frames: sky-subtracted, fully calibrated frames, in integer format. They can be retrieved at the above WWW address, where a request form will be available. The requests will be handled by the Science Archive Group. 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 can be found at "''.

Coadded sections: sky-subtracted, fully processed (see above) sections of the coadded image. 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 an HCOMPRESS library originally written by White (1992) for the STScI. The coadded sections have been compressed using a very high compression scale of 200. 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). The size of the original images is 67 MB, whereas that of the compressed and re-sampled images is about 150 kB. These sections are handled by an on-line server, similar to that available for the Digitized Sky Survey (DSS). A preliminary object catalog, containing only position and shape information is also available on the on-line server. For the display of the sections and the catalog SkyCat can be used as an interface.

Low-resolution coadded image: sky-subtracted, fully processed coadded image. This image is meant to give a general overview of the whole patch and it has been produced by re-binning (3 arcsec pixel size) and pasting together the sections. This is a standard output of the pipeline. This image ($\sim$25 Mb) can be retrieved at the same web page as above.

Single frame catalogs: Object catalogs associated with each single frame. A full description of the parameters available is presented below. The name convention of the catalogs is based on that of the EIS tiles Ai,j (see Sect. 2). The catalogs are in binary FITS table format.

Note that the coadded sections and image currently available are not suited for astronomical reduction because of the varying noise properties and compression, but are useful for proposal preparation and comparison with EIS catalogs or other data sets.

The main difference between the current release and the final release of the EIS data is that the latter will also include the coadded image and the auxiliary weight and context maps, as well as the final object catalog which will contain information about the context within which a given object has been identified. The inclusion of the context information into the catalog extracted from the coadded image is currently underway.

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