DR4 Release - July 1st 2008
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:
Particular attention should be given to any notes detailing limitations
and known issues - see below,
known issues and
- 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.
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
- 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
- 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
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
DR4 Release Summary
||No. of multiframes
||No. of objects in
|No. of sources in
||Y=20.2, J=19.6, H=18.8, K=18.2
||J=19.8, H=19.0, K=18.1
||Z=20.4, Y=20.1, J=19.6, H=18.8, K=18.2
WFAU, Institute for Astronomy,
Royal Observatory, Blackford Hill
Edinburgh, EH9 3HJ, UK