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The Australia Telescope National Facility Colloquium
15:30-16:30 Wed 21 Jan 2004

ATNF Marsfield Lecture Theatre

Dr. Matthew Whiting

(Department of Astrophysics & Optics, School of Physics, University of New South Wales)

What made the quasar blush? Optical properties of radio quasars. - Dr. Matthew Whiting Colloquium

Quasars selected at radio frequencies are known to have different
optical properties, redder colours for instance, to those selected in
the optical/UV. In this talk, I present a model to explain the different
optical colours of radio-selected quasars. This model involves a
contribution from the relativistic jet that powers the radio emission.
We find that both the accretion disc and the jet emission are important
contributors to the optical/NIR emission, and that the contribution from
the jet accounts for the much of the observed colour distribution.
I will also discuss the properties of quasar-like sources known as BL
Lac Objects, how they relate to the quasars in our sample, and how their
optical properties can give clues about the accretion and outflow
processes occuring close to the super-massive black hole believed to be
Finally, the relationship of quasars and BL Lacs with optically
"passive" radio galaxies will be discussed, particularly the
implications for radio surveys that extend to fainter flux limits.

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