THE FIRST RADIO-LOUD BROAD ABSORPTION-LINE QSO AND EVIDENCE FOR A HIDDEN POPULATION OF QUASARS

We have discovered two low-ionization broad absorption line (BAL) quas ars in programs to obtain optical spectra for radio-selected quasar ca ndidates from the VLA Faint Images of the Radio Sky at Twenty Centimet ers (FIRST) Survey. Both belong to the extremely rare class of BAL QSO s that exhibit narrow absorption lines from metastable excited levels of Fe II and Fe III. Until now, there was just a single object in this class, 0059-2735. In addition, one of our new objects is the first kn own radio-loud BAL QSO. The properties of these three unusual objects suggest a trend of increasing radio luminosity with the amount of abso rption to the quasar, and are perhaps transition objects between radio -loud and radio-quiet quasars. The two new objects are from a radio-se lected sample comprising less than 200 quasars; one is heavily attenua ted at optical wavelengths in the observed frame. These objects would be easily overlooked by most optical QSO searches; their abundance in the radio sample suggests that they may be representatives of a largel y undetected component of the quasar population, perhaps as numerous a s ordinary low-ionization BAL QSOs, which constitute 1%-2% of all QSOs .