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VLBApls source sample

VLBApls source sample definition

1. The VSOP Survey Continuum Source List

The radio sample for the VSOP continuum survey was defined to include all extragalactic radio sources with:

a total flux density at 5 GHz, S>=1.0 Jy
a spectral index alpha>=-0.5
a galactic latitude |b|>=10°

The sample was compiled in large part from the Green Bank GB6 Catalog (Gregory et al. 1996, ApJS 103, 427) and the Parkes-MIT-NRAO PMN Survey (Lawrence et al. 1986, ApJS 61, 105; Griffith & Wright 1993, AJ 105, 1666). Because of the variability of most compact radio sources, the total flux density and spectral index criteria for inclusion of a source in the sample was imprecise because of the large time range between the observations in the search catalogs. We included a source in the sample if any of the relevant catalog observations found the source stronger than 1.0 Jy, and if the compact part of the radio emission met the spectral index and galactic latitude critera. We adopted this liberal approach of inclusion in the sample since it is easier to remove unwanted sources than to include (after the observations) sources which were missed. The sample also included all sources in the sky with a 5 GHz flux density S>5 Jy, regardless of spectral index and galactic latitude. These sources were not in the 'formal' sample, but were also important for study.

The VSOP continuum source list contains 402 sources. Fifty of the sources have a spectral index somewhat less than -0.5 or lie within 10° of the galactic plane, and are not part of the 'complete' sample as defined above.

2. The VLBApls Source List

The goal of the VLBA observations was to determine which of the sources in the VSOP continuum list were sufficiently strong on the longest VLBA baseline (usually MK-SC, Mauna Kea to Saint Croix) for probable detection in a typical HALCA observation (detection level is ~0.1 Jy). For this reason we observed sources with the VLBA as far south as -44° where such information could be obtained. We also included 22 additional sources which were known to be highly variable but not included in the preliminary VSOP list in order to determine if their flux density in June 1996 was greater than 1 Jy. The source would then be included in the VSOP sample (three of the sources were found with a flux density above 1 Jy and added to the sample).

The VLBApls home page (and Table 1 of the paper) contains the list of 374 sources reported in the paper. This sample consists of 355 of 357 sources from the VSOP survey source list north of declination -44°, plus 19 sources with S<1.0 Jy.

VLBApls home page
Last modified: 17 Oct 2000