Cadenced IRAC Monitoring of Infrared-Variable AGNs
Abstract
We have analyzed IRAC imaging data from 87 Spitzer visits to a very well-studied field, the IRAC Dark Calibration Field (IRAC-CF) near the north ecliptic pole. With this extensive dataset we have already identified a unique sample of 40 infrared-variable galaxies which we are now working to characterize with respect to variability amplitudes and timescales, panchromatic SEDs, and host morphologies, among other quantities. Unfortunately, we have found that the continual change in the spacecraft roll angle means that our sources are typically observed for at most six months at a time by each IRAC FOV in succession -- in other words, the visibility windows are exactly out of phase. Thus the existing data, despite the fact that they extend over more than three years starting in 2003 December, present large, unavoidable gaps that frustrate the time-delay analysis we wish to perform on exactly the timescales known to be common in active galaxies. Such an analysis, especially for a sizable, unbiased sample such as we now have, holds unique promise for measuring the colors and temperatures of infrared-varying AGN, and will have much to say about the underlying physical models of the infrared AGN emission. Accordingly we ask for just 10 h to gather IRAC photometry in the gaps that would otherwise accrue in Cycle 4.
- Publication:
-
Spitzer Proposal
- Pub Date:
- May 2007
- Bibcode:
- 2007sptz.prop40553A