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EDRplus and EDR Release - February 10th 2006

The EDR and EDRplus data products are described in the UKIDSS Early Data Release paper. The EDR provides a small sample dataset (about 1% of the whole of UKIDSS) that is representative of the quality of future survey releases. In addition the EDRplus dataset contains data of similar quality but where the full filter complement of a particular survey is unavailable. The charts linked below reflect the status of the UKIDSS surveys in the UKIDSS EDRplus release. A description of the data and how it is held in the archive is given in the data overview.

Particular attention should be given to the following notes detailing limitations and bugs (see also generic issues and bugs noted under Known Issues): KNOWN BUGS:

  • Co-averaging of the deep stacks in the DXS is subject to digital quantisation noise because the standard pipeline processing software uses integer representation of pixel ADUs. Sky noise estimation at the catalogue extraction stage is also affected by this, and the knock-on effect is that the deep stack images and catalogues in the DXS are not optimal in terms of depth. This problem does not affected the UDS deep stacks, because these were co-added and use floating point representation for the pixel ADUs.
  • For the UDS deep stacks, weight images were converted to confidence images and the scaling was done independently for each of four overlapping sub-images created from a single, large mosaic. These independently scaled confidence images lead to an overestimation in the noise of around 20%, hence the UDS catalogue error attributes are overestimated by a similar amount.
  • The catalogues produced from the overlapping UDS frames have not been correctly seamed, so there are unflagged duplicate images in the UDS source catalogues. FIXED: 15 FEB 2006
  • Science-verification data from the DXS has been included in the EDR. Unfortunately, at the source merging stage the science verification stacks were not included, so the DXS merged source catalogue does not contain merged sources for all available fields. FIXED: 15 FEB 2006
  • Incomplete JK frame sets in the DXS have not been purged in the EDR subset, so the EDR and EDRPLUS datasets are identical for the DXS. FIXED: 15 FEB 2006
  • In creating the EDR, all frame sets having incomplete filter coverage have been removed (they remain in the EDRPLUS). This applies to all stack image, single-passband catalogue detections derived from them and merged source data. Note however that the ancestor images of these stacks (e.g. normal and interleaved frames and their corresponding confidence images) still remain in the EDR database.
  • There are a variety of image defects in the pixel data that may give rise to spurious catalogue detections with unusual colours. These result from, amongst other things, cross-talk images and persistence images (see Dye et al. for further details).

  • August 23rd 2006 UDS catalogues removed from the EDR and EDRPLUS databases since they are highly sub-optimal, and are superseded anyway by the newly available DR1

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