The physical nature of the blue objects in the field of BD +15 2469 (Virgo Cluster).

Low-dispersion objective-prism spectra obtained with the UK and Tautenburg Schmidt telescopes are used to characterize 277 objects with UV excess (magnitude 15-18; U-B less than -0.2) in the third 22-sq-deg Virgo-cluster field of the Asiago survey of blue faint objects (Barbieri and Benvenuti, 1974). The results are presented in tables and graphs. The distribution of objects is found to be 43 percent hot stars, 39 percent F and G stars, 3 percent white dwarfs, 7 percent compact galaxies, and 8 percent quasars, but the proportions change with decreasing U-B. The surface densities for certain quasars and for certain and supposed quasars are given as 0.49 and 0.98/sq deg, respectively.