Spitzer Space Telescope - General Observer Proposal #3624


Unified Models and Power Sources in Radio-Loud AGN

Principal Investigator: Robert Antonucci
           Institution: University of California, Santa Barbara

Co-Investigators: 
Patrick Ogle, NASA / JPL                                              
David Whysong, University of California, Santa Barbara                

Science Category: AGN/quasars/radio galaxies 
 Observing Modes: IrsStare 
  Hours Approved: 27.0 

Abstract:
We propose a simple observational program that will test the
unification hypothesis for quasars and FR-II radio galaxies, constrain
models of the dusty torus, and determine if the AGN are powered by
thermal accretion or a non-thermal (probably rotational) mechanism.
Spitzer is uniquely capable of carrying out this investigation with
its unprecedented sensitivity.  It has been shown directly by optical
spectropolarimetry that many of the most powerful FR-II radio galaxies
contain quasars hidden by opaque dusty tori;  there is substantial
statistical evidence that this is true for most or all of them.  At
somewhat lower powers the situation is not yet clear.  Our work and
that of others suggests that only a subset of radio galaxies have
hidden quasars.  We seek to establish this one way or the other and to
determine which radio galaxies do or do not have hidden quasars.
Spitzer data will also clarify whether statistical anomolies
associated with the identification of radio galaxies with quasars can
be understood as effects of a large population of physically smaller
radio galaxies that lack hidden quasars.  This would limit and define
the applicability of the Unified Model.  For theory, it would
determine whether there are black-hole powered sources with just
kinetic luminosity and without significant radiative accretion
luminosity .  Such non-thermal AGN would then have to be attributed to
tapping rotational energy.  We will also examine and compare the other
observational properties of the two types of radio galaxies (hidden
quasar or not), providing insight into the physics of the two types of
power (accretion and rotation).