Engelbracht, C. W. and Blaylock, M. and Su, K. Y. L. and Rho, J. and Rieke, G. H. and Muzerolle, J. and Padgett, D. L. and Hines, D. C. and Gordon, K. D. and Fadda, D. and Noriega-Crespo, A. and Kelly, D. M. and Latter, W. B. and Hinz, J. L. and Misselt, K. A. and Morrison, J. E. and Stansberry, J. A. and Shupe, D. L. and Stolovy, S. and Wheaton, Wm. A. and Young, E. T. and Neugebauer, G. and Wachter, S. and Pérez-González, P. G. and Frayer, D. T. and Marleau, F. R. (2007) Absolute Calibration and Characterization of the Multiband Imaging Photometer for Spitzer. I. The Stellar Calibrator Sample and the 24 μm Calibration. Publications of the Astronomical Society of the Pacific, 119 (9). pp. 994-1018. ISSN 0004-6280 http://resolver.caltech.edu/CaltechAUTHORS:ENGpasp07
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We present the stellar calibrator sample and the conversion from instrumental to physical units for the 24 μm channel of the Multiband Imaging Photometer for Spitzer (MIPS). The primary calibrators are A stars, and the calibration factor based on those stars is MJy sr^−1 (DN s^−1)^−1, with a nominal uncertainty of 2%. We discuss the data reduction procedures required to attain this accuracy; without these procedures, the calibration factor obtained using the automated pipeline at the Spitzer Science Center is lower. We extend this work to predict 24 μm flux densities for a sample of 238 stars that covers a larger range of flux densities and spectral types. We present a total of 348 measurements of 141 stars at 24 μm. This sample covers a factor of 460 in 24 μm flux density, from 8.6 mJy up to 4.0 Jy. We show that the calibration is linear over that range with respect to target flux and background level. The calibration is based on observations made using 3 s exposures; a preliminary analysis shows that the calibration factor may be 1% and 2% lower for 10 and 30 s exposures, respectively. We also demonstrate that the calibration is very stable: over the course of the mission, repeated measurements of our routine calibrator, HD 159330, show a rms scatter of only 0.4%. Finally, we show that the point-spread function (PSF) is well measured and allows us to calibrate extended sources accurately; Infrared Astronomy Satellite (IRAS) and MIPS measurements of a sample of nearby galaxies are identical within the uncertainties.
|Additional Information:||© 2007. The Astronomical Society of the Pacific. Received 2006 November 15; accepted 2007 July 25; published 2007 September 28. We thank John Carpenter for helpful discussions, especially regarding the effect of exposure time on the measured count rate. We would also like to thank the anonymous referee, whose comments improved this paper. This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under NASA contract 1407. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. Support for this work was provided by NASA through contract 1255094 issued by JPL/Caltech.|
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