Faint blue objects at high Galactic latitude. VIII. Performance characteristics of the US survey

The US survey has cataloged 3987 objects in seven high Galactic latitude fields according to their optical colors, magnitudes, and morphologies using photographic techniques. This paper analyzes the effectiveness of the survey at producing finding lists for complete samples of hot stars and quasars that exhibit blue and/or ultraviolet excess (B-UVX) relative to the colors of halo F and G subdwarf stars. A table of 599 spectroscopic identifications summarizes the spectroscopic coverage of the US objects that has been accomplished to date. In addition, some of the survey plates have been reexamined for objects missed during the original selection, and the literature has been searched for all other spectroscopically identified blue stars and quasars with z < 2.2 that have been selected by other surveys within the US survey areas. These results are used to estimate empirically both the accuracy of the US survey selection boundaries ( in color, morphology, and brightness) and the completeness of the resulting samples of B-UVX US objects within those boundaries. In particular, it is shown that the reliability of the US color classifications is high and that the previously derived US morphological boundary for the complete selection of unresolved quasars is accurate. The contribution of color and morphological classification errors to B-UVX sample incompleteness is therefore correspondingly small. The empirical tests indicate high levels of completeness (95(-2)(1)%) for the samples of US quasars and hot stars isolated within the stated survey selection limits. Errata and improvements to some of the published catalog data are presented in Appendices.