This is the first paper in a series about our Multiwavelength Quasar Survey. We give a detailed description of this survey and present the scientific objectives, candidate selection procedures, and initial results of the observations of X-ray candidates in field f1002. Multiwavelength methods are employed in order to reduce the selection effects. In this survey, we hope to get a quasar sample more complete than that of any previous survey.

The region of the Virgo cluster is the subject of an intensive quasar search, since quasarswill provide valuable probesof absorption due to galaxy haloes and the intracluster medium. This paper presents data for 17 quasar candidates which have been observed spectroscopically, 15 of which are confirmed as quasars. With more than half of the emission-line and ultraviolet excess candidates niow boserved, the overall success rate for detecting quasars is ～80 per cent. There appears to be a deficiency of quasars in the Virgo field by a factor of 2, when compared to other regions studied with the same technique. The distribution of quasars in Virgo has been compared with the galaxy distribution, using the most recent catalogue. There is no evidence for association between the no evidence of clustering among the quasars. One of the aims of this project is to provide a complete sample of bright quasars for absorption-line studies with the Space Telescope. Only two quasars have lines-of-sight that pass through galaxy discs, but 10 quasars have lines-of-sight that pass through halo material, if haloes around cluster galaxies have the size indicatedby the statistics of quasar absorption-line systems. Anothersource of absorbing material is the set of extremely low surface brightness dwarf galaxies that have recently been found on contrast-enhanced Schmidt plates of the Virgo region.

Ten new members of the class of compact extragalactic H II regions or blue compact dwarf galaxies (BCG) have been discovered in the directon of the Virgo cluster using objectiveprism plates from the UK Schmide Telescope. Follow-up spectroscopy of fieve of the new galaxies shows them to be low-luminosity systems (-14≥MV≥-19) with strong narrow lines of large equivalen width. Velocities of three of the galaxies show them to be in the Virogo cluster. Form plots of line rations which separate objects according to excttation mechanis, there is no eveidence for power-law excitation or broad line components in any of the galaxies. Selection of BCGs form UK Schmide plates is particularly well suited to the discovery of ultra-low-luminosity galaxies where the intense star formation is concentrated in one region.

Summary. Using objective-prism plates taken with the 44-arcmin objective prism mounted on the UK Schmidt telescope, we have found 53 emission-line quasar candidates and 29 ultraviolet-excess objects (possible low-redshift quasars) in a 5x5 degree2 field centred on 12h27m, +13°30' (1950) in the Virgo cluster of galaxies. Eighteen of these 82 candidates were observed using the double spectrograph on the Palomar 5-metre telescope; 13 of the observed objects proved to be quasars. The broad-absorption-line QSO Q1232+134 is the first example of the class to show broad low-ionization absorption lines- such as Mgnλ2798A-in addition to the usual high-excitation lines such as NλA 1240 A. Although we find no conclusive evidence for quasar-galaxy associations in this field, there do exist non-uniformities in the distribution of the quasar candidates, which may merit further investigation. These objects will provide a useful network of probes for absorbing material in the Virgo cluster. The lines-of-sight to two of the confirmed quasars pass very close to NGC galaxies; the respective projected QSO-galaxy separations are only 4 and 11kpc at the assumed distance of the Virgo cluster.

Using the up-dated observational data of quasars in the Virgo cluster region, we analyze the two-dimensional distribution of quasars and the association between the quasars and the galaxies in the Virgo region. The clustering of quasars and the gravitational lense effect from the Virgo cluster are tested. The results showed that: (1) the association of the quasars and the bright galaxies in the Virgo cluster is not significant; (2) the quasars' distribution in the region shows weak clustering; (3) the gravitational lense apparently effect on the luminosity function.