Spitzer Space Telescope - Archive Research Proposal #30390


Mid-Infrared Variability from AGN in the IRAC Dark Field:  Photometric
Refinement, Discovery, and Characterization

Principal Investigator: Jason Surace
           Institution: SIRTF Science Center

Co-Investigators: 
Varoujan Gorjian, JPL                                                 
Mark Lacy, Spitzer Science Center/Caltech                             
Lin Yan, Spitzer Science Center/Caltech                               

Science Category: AGN/quasars/radio galaxies 
Dollars Approved: 46910.0 

Abstract:
We request archival funding to support an investigation into the
mid-infrared variability of AGN discovered in the IRAC Dark Field.
The requested funding is needed to refine the photometric accuracy of
the IRAC calibration as a function of both array position and time,
allowing detection of much smaller effects than could be achieved from
the SSC pipeline data products.  As part of this we propose to use
more sophisticated search techniques to expand the range of detectable
variability to smaller amplitudes and timescales than we have already
found.  This may also uncover supernova signatures and other periodic
variations.  The field itself is an extragalactic field 15 arcminutes
in diameter near the north ecliptic pole, and is the dark current
calibration target for IRAC.  Because it is observed frequently as
part of routine operations, it is now similar in size and depth to the
infrared component of the GOODS program, and is confusion-limited in
the mid-infrared.  More importantly, due to the periodicity of the
observations, the Spitzer data are sensitive to variability on week
timescales, ultimately spanning a baseline of five to seven years, and
are the only mid-infrared dataset that will have this capability at
this depth for the foreseeable future.  This work will have a
significant impact on other studies both by producing a comprehensive
look at variability in deep mid-IR surveys, and also through the
development of advanced data reduction techniques that can be applied
to other programs for the purpose of refining IRAC's relative
photometric accuracy.