On the absence of radio-loud BALQSOs

Previous abstract Next abstract

Session 105 -- Broad Absorption Line Quasars
Display presentation, Saturday, January 1, 9:30-6:45, Salons I/II Room (Crystal Gateway)

[105.03] On the absence of radio-loud BALQSOs

Martijn de Kool (Max Planck Institut f\"ur Astrophysik)

It is proposed that the observed absence of radio-loud broad absorption line QSOs can be naturally understood as an orientation effect, if broad absorption lines are only visible in QSOs in which the line of sight to the continuum source passes close to an accretion disk. Compact, flat spectrum radio loud quasars are generally thought to contain a jet pointing in the direction of the observer. Since the jet will be perpendicular to the accretion disk, the line of sight to the active nucleus will never pass through the broad absorption line region (BALR) in such objects. Extended, steep spectrum radio loud quasars are not as strongly beamed, but it is shown that the number of such objects expected in the sample of 68 BALQSOs with good radio observations is only $\sim 1$. It is not as straightforward to account for the absence of BALQSOs from a sample of $\sim 50$ high-$z$ steep spectrum radio loud quasars, but it is argued that a moderate amount of beaming in the extended emission could introduce selection effects that explain this observation. The recently discovered high incidence of BALQSOs among radio-moderate QSOs fits into this scheme if the radio-moderate population is interpreted as consisting of intrinsically radio-loud systems which appear weak because the jet is almost perpendicular to the line of sight. In this case the chance that the line of sight lies close to the accretion disk, and thus passes through the BALR, is significantly enhanced.

Saturday program listing