FIRST Survey 95Jan06 Catalog

This is the description of the 1995 January 6 FIRST catalog. It has been replaced by a newer catalog. Old released versions of the FIRST catalog are made available for archival purposes for the benefit of those who have already started research programs based on those catalogs. The newest version is always preferred for new projects.

See the catalog history for information on changes in the various FIRST catalogs.

A catalog containing 26,892 sources from the 1993 observations is currently available as a compressed ASCII file (catalog_95jan06.bin.Z). Please be warned that this is not a final catalog; it is being made available as a service to the astronomical community, but it still has some shortcomings.

There are a small number of regions near bright, complex objects where some catalog entries are due to sidelobes rather than to real sources. We know of only 7 fields (of 1039) that may be affected by this problem: 08390+28521, 10000+28521, 10030+28521, 11150+29486, 12060+30456, 13540+30456, and 15030+28521. These fields are mainly on the extreme northern or southern edges of the survey area. Users of the current catalog should beware of sources from these fields.
About 5% of the fields contain a bright source that leads to an increased noise level in the maps and so an increased flux density limit for source detection. In a few fields the noise is markedly worse; this is especially noticeable near 3C 286 (F~15 Jy, RA = 13h 31m 8.2s, Dec = 13d 31' 33"), which effectively wipes out a large area in its vicinity. The final catalog will include a complete description of the sensitivity as a function of position in the sky.
The flux densities in the catalog are systematically too low by about 0.25 mJy due to the ``CLEAN bias'' effect (see our Astrophysical Journal paper for more details). The bias is larger in noisy fields. A more detailed model of this effect will be included in the final catalog.

The catalog is sorted by right ascension and has the following format:

    RA  (2000)   Dec         Fpeak      Fint    RMS    Maj   Min   PA  Field Name
07 14 46.828 +30 49 57.18     1.94      2.73   0.139   4.8   1.8  91.3 07150+30456
07 14 50.117 +30 38 12.77     5.39      4.90   0.150   0.0   0.0   0.0 07150+30456
07 14 55.492 +30 44 28.42     0.99      0.98   0.131   0.0   0.0   0.0 07150+30456
07 14 55.951 +30 41 28.81     0.77      1.49   0.134   6.4   4.0 160.2 07150+30456
07 15 11.496 +30 38 57.21    35.61     40.99   0.139   3.0   0.4  57.9 07150+30456

Fpeak, Fint, and RMS are the peak flux density, integrated flux density, and a local noise estimate at the source position, all measured in mJy. Maj, Min, and PA give the major and minor axes (FWHM) and position angle (degrees east of north) of an elliptical Gaussian model for the source. The Field Name is the name of the coadded image (available through several archives) containing the source.

Richard L. White, rlw@stsci.edu
1996 May 28