The Molonglo Reference Catalog 1 Jy radio source survey. III. Identification of a complete quasar sample

We present a new complete sample of 111 radio quasars (including six BL Lac objects) selected from the Molonglo Reference Catalog (MRC) at 408 MHz. The sample, which we call the Molonglo Quasar Sample (MQS), forms part of a complete survey of 557 MRC radio sources with S-408 greater than or equal to 0.95 Jy in the declination range -30 degrees < delta < -20 degrees, b > 20 degrees but excluding the R.A. range 14(h)03(m)-20(h)20(m). Quasar classifications are based on high-resolution radio images, deep optical identifications, and follow-up spectroscopy of sources in the strip. The relatively low radio frequency of the finding survey and the complete optical identification of quasars to faint magnitudes ensure that the MQS is relatively free from orientation biases that affect most other samples of radio-loud quasars. The MQS is therefore particularly well suited to investigating the effects of radio axis orientation on quasar properties. This paper describes in detail the formation of the MQS and presents basic radio and optical data, including VLA images of extended radio sources in the sample and a complete set of optical finding charts.