The Transition from 'Normal' to 'Broad Absorption Line Quasar' of Ton 34

摘要

We report the emergence of a high velocity, broad absorption line outflow inthe luminous quasar Ton 34, at z=1.928. The outflow is detected through anultraviolet CIV broad absorption line, in a spectrum obtained in January 2006by the Sloan Digital Sky Survey. No absorption trough was present in twodifferent spectra acquired in 1981 at Las Campanas and Palomar observatories,indicating the emergence of the outflow in less than ~8 yr (rest-frame). Theabsorption line spans a velocity range from ~5,000-26,000 km s-1}, andresembles typical troughs found in Broad Absorption Line quasars (BALQSOs). Wemeasure a balnicity index >600 (tough this value might be an underestimationdue to a conservativeplacing of the continuum). The absorption trough is likelysaturated, with the absorbing gas covering ~25% of the emitting region. Weexplore different scenarios for the emergence of this outflow, and find anexisting wind moving across our line of sight to the source as the most likelyexplanation. This indicates that high velocity outflows (producing broadabsorption troughs in BALQSOs) might be ubiquitous in quasars, yet only becomeobservable when the wind accidentally crosses our line vision to the centralsource.