Extragalactic abstracts - IRSA - California Institute of Technology

Spitzer_Approved_Extragalactic
Mar 25, 10 16:24 Page 427/742
Spitzer Space Telescope − Theoretical Research Proposal #40095
The AGN Obscuring Torus
Principal Investigator: Moshe Elitzur
Institution: University of Kentucky
Technical Contact: Moshe Elitzur, University of Kentucky
Science Category: AGN/quasars/radio galaxies
Dollars Approved: 90870.0
Abstract:
The generally held view of active galactic nuclei (AGN) is that of a
supermassive black hole surrounded by an obscuring toroidal structure, with much
of the AGN observed diversity simply explained as the result of viewing this
axisymmetric geometry from different angles. The torus consists of a large
number of individually very optically thick dusty clouds which absorb a fraction
of the nuclear luminosity and re−radiate it in infrared. However, because of
theoretical difficulties, models of the torus IR emission traditionally employed
smooth density distributions. We have recently developed the basic formalism for
handling dusty cloud distributions, and our clumpy torus models have already
been utilized successfully in analysis of Spitzer observations. This proposal
requests support for the implementation of a full treatment of the dust grain
mixture in our torus model calculations. From the results we will find the
variation in dust composition and abundance in clouds across the interface
between the torus and the broad lines region, and provide detailed model
predictions for the reverberation response in near−IR and emission line
spectrum. This will open up a new type of analysis, in which Spitzer
observations are combined with reverberation measurements to shed light on the
origin and dynamics of clouds around the AGN central black−hole. The results of
this proposal will be incorporated into a web site that enables users to fit IR
observations with clumpy torus models with their own sets of input parameters.
Spitzer_Approved_Extragalactic
Printed_by_SSC
Mar 25, 10 16:24 Page 428/742
Spitzer Space Telescope − General Observer Proposal #3551
Unravelling the Nature of Dusty Tori in Radio−Loud Active Galactic Nuclei
Principal Investigator: Martin Elvis
Institution: Harvard−Smithsonian Center for Astrophysics
Technical Contact: Martin Elvis, Harvard−CfA
Co−Investigators:
Hermine Landt, Harvard−Smithsonian Center for Astrophysics
Moshe Elitzur, University of Kentucky
Science Category: AGN/quasars/radio galaxies
Observing Modes: IracMap IrsStare MipsPhot
Hours Approved: 8.0
Abstract:
The lack of broad emission lines in some narrow−line active galactic nuclei
(AGN) has been explained by orientation effects: an optically thick, dusty torus
obscures the broad emission line region in AGN oriented at large angles with
respect to our line of sight. However, details of the physical state of the
obscuring torus remain little known to this day. In fact, recent models indicate
that the obscurer is possibly made up of a few clouds instead of having a
continuous density distribution. An effective way to test present models is
based on their distinct predictions for the inclination angle dependence of the
emitted infrared spectral energy distribution (SED) and the 10 micron silicate
feature. Here we propose a total of 8.2 hrs with the Spitzer Space Telescope in
order to map the infrared SED with IRAC and MIPS and the depth of the 10 micron
silicate feature with IRS for 12 radio−loud AGN with known inclination angles
(range 20 − 60 deg). Having elliptical galaxy hosts these AGN will not have a
starburst as a major contaminant of their far−infrared emission. Our
observations will allow us to constrain the filling factor, scale and geometry
of the obscurer in AGN. The result will be a deeper understanding of AGN.
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