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DR4 Release - July 1st 2008

Important note:

Oct 30th 2008 - The GPS was added to the UKIDSS DR4 release

Please see UKIDSSDR3PLUS for UDS data. A new UDS mosaic is in preparation and will be included in this database at a later date.

Issues fixed in DR4:

  • The calculation of the dither offset that defines the underexposed region of stacked images has been revised. Previously this quantity was underestimated in some LAS and DXS passbands, so the affected flags have now been recalculated. This was for all surveys, though only the LAS and DXS data will show a noticeable increase in the number of sources flagged as being in the underexposed region.
Particular attention should be given to any notes detailing limitations and known issues - see below, known issues and data overview.

New in DR4:

There are several new features in this release. These include
  • Photometric data in detection tables now contain the field distortion and illumination corrections (see CASU pages), for all shallow stack data. Photometric data from deep stacks include the field distortion corrections, but no illumination corrections and photometric data from mosaics will not include either correction.
  • The *Detection tables now include a default row for every detector frame. Whereas prior to DR4 there was one row with all attributes default in *Detection, now there is a row for every combination of non-default (multiframeID,extnum) with all other attributes default. The reason for this change, and potential pitfalls when writing queries that make joins between *Source and *Detection, are explained here.
  • There are additional attributes, Multiframe.illumFile and MultiframeDetector.totalExpTime. Multiframe.illumFile will contain the file name of the CASU illumination table used to correct a given multiframe. Currently this is set to default, but will be updated at a later date. The illumination tables are calculated on a monthly basis by CASU. As such there are no illumination corrections for deep stacks and mosaics; thus the illumFile entry for these products will always be default. The MultiframeDetector.totalExpTime value is calculated for all stacks. For shallow stack data it is simply the product of the number of jitters, the number of microsteps and the exposure time. For deep stacks it is the sum of the totalExpTime of all intermediate stacks that went into the deep frame. Mosaics are calculated in the same way as deep stacks, but then the value is divided by the number of pointings. The totalExpTime is an indicator of the depth of the field in question. It is in MultiframeDetector, since some frames have problems with individual extensions, so a deep stack could have different depths depending on the extension in question.
  • The LAS is now cross-matched to the SDSS Segue DR6 catalogue.

The charts linked below show the status of the UKIDSS surveys in this release. This fourth release, like the DR3plus release, only contains one database, DR4plus, which contains all the data, i.e. includes data from fields that have incomplete waveband coverage as prescribed by a given survey. The WSA DR4plus release contains views of the survey source tables that allow users to easily target their queries at only those areas that have complete waveband coverage. The names of the source table views are lasYJHKsource, gpsJHKsource, gcsZYJHKsource and dxsJKsource. These names reflect the required waveband coverage. They appear in the schema browser under both the table and view sections. The UDS being only one field that now has coverage in J, H and K does not require a view.

A description of the data and how it is held in the archive is given in the data overview.

DR4 Release Summary

Survey No. of multiframes No. of objects in
detection table
No. of sources in
source table
Approximate depths Plots
LAS 288,097 83,533,424 40,081,446 Y=20.2, J=19.6, H=18.8, K=18.2 link
GPS 203,668 988,424,311 554,786,690 J=19.8, H=19.0, K=18.1 link
GCS 94,571 69,333,650 37,074,213 Z=20.4, Y=20.1, J=19.6, H=18.8, K=18.2 link
DXS 178,756 10,796,379 1,286,205 J=20.9-22.4,K=19.2-21.2 link
UDS 81,038 initially 0 initially 0   link

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