NOTE: This page provides details specific to this data release. Please look at common ground for more information. ALL data will be reprocessed uniformly at the end of the survey.

At this time we are releasing 10 more subfields: the remaining 5 subfields in F4, and 5 subfields in F2.

Third Release (December 2003)

Subfield	Catalog	FITS Images	JPEG (from BVR)	JPEG (from Rz)
F2p13	F2p13.cat.gz	B , V , R , z'	F2p13BVR.jpg (~ 3.0 MB)	F2p13Rz.jpg (~ 2.5 MB)
F2p21	F2p21.cat.gz	B , V , R , z'	F2p21BVR.jpg (~ 3.0 MB)	F2p21Rz.jpg (~ 2.5 MB)
F2p31	F2p31.cat.gz	B , V , R , z'	F2p31BVR.jpg (~ 3.0 MB)	F2p31Rz.jpg (~ 2.5 MB)
F2p32	F2p32.cat.gz	B , V , R , z'	F2p32BVR.jpg (~ 3.0 MB)	F2p32Rz.jpg (~ 2.5 MB)
F2p33	F2p33.cat.gz	B , V , R , z'	F2p33BVR.jpg (~ 3.0 MB)	F2p33Rz.jpg (~ 2.5 MB)
F4p12	F4p12.cat.gz	B , V , R , z'	F4p12BVR.jpg (~ 3.0 MB)	F4p12Rz.jpg (~ 2.5 MB)
F4p13	F4p13.cat.gz	B , V , R , z'	F4p13BVR.jpg (~ 3.0 MB)	F4p13Rz.jpg (~ 2.5 MB)
F4p23	F4p23.cat.gz	B , V , R , z'	F4p23BVR.jpg (~ 3.0 MB)	F4p23Rz.jpg (~ 2.5 MB)
F4p31	F4p31.cat.gz	B , V , R , z'	F4p31BVR.jpg (~ 3.0 MB)	F4p31Rz.jpg (~ 2.5 MB)
F4p32	F4p32.cat.gz	B , V , R , z'	F4p32BVR.jpg (~ 3.0 MB)	F4p32Rz.jpg (~ 2.5 MB)

There have been some changes in image processing compared to previous releases. We are now using sinc interpolation when shifting the images to be stacked (first two releases used bilinear). In R, the filter we always observe in when seeing is good, this results in a measurably sharper image. In BVz, the seeing may be poor enough that the resolution is not much improved.

In the first and second data release we used a "little trick" to clean our SExtractor catalogs from junk around bright stars. We found that this cleaning can be done in an automatic and pretty effective way by requiring ellipto errcode of 0 (Bernstein and Jarvis, AJ 123, 583, 2002), so we filtered for that before posting catalogs to the public. For the second release, we applied the errcode==0 criterion to each separate catalog, and then matched, which means that only information from a bands with errcode zero was released. For example, if an object was detected in B with ellipto errcode==0, in V also with errcode==0, in R with errcode==2, and simply not detected in z, only the BV information was released. However, we have since recognized that this strict criterion for measuring shapes cleanly results in too many lost objects in crowded regions.

In this third release, we use SExtractor (version 2.1.6) using the parameter files default.sex, default.nnw, and default.conv to detect objects separately in each filter (as we did in the second release). We then match the BVRz catalogs, and eliminate objects which have ellipto errcode!=0 in all filters. In other words, we require ellipto errcode==0 in at least 1 band, but given that, we release information from all other bands where a detection occurred (even if errcode is nonzero). The information in BV and R from the example above would be included in catalogs from this third release.

The format of the catalogs is the same as for Release 2, with the addition of CLASS_STAR, a SExtractor star/galaxy classification parameter. The catalog for each subfield is contained in a gzipped ascii file, one object per line, with the following space-separated columns:

The columns are listed once for each photometric band in the order BVRz'.

Known issues: Catalogs may be missing objects in crowded regions. See the fifth question in the Data Release FAQ. (This effect was already present, but not seriously recognized, in previous data releases.)