Asteroidscomets

Spitzer IRAC Photometry of JWST Calibration Stars

April 2021 • 2021AJ....161..177K

Authors • Krick, Jessica E. • Lowrance, Patrick • Carey, Sean • Laine, Seppo • Grillmair, Carl • Van Dyk, Schuyler D. • Glaccum, William J. • Ingalls, James G. • Rieke, George • Hora, Joseph L. • Fazio, Giovanni G. • Gordon, Karl D. • Bohlin, Ralph C.

Abstract • We present infrared photometry of all 36 potential JWST calibrators for which there is archival Spitzer IRAC data. This photometry can then be used to inform the stellar models necessary to provide absolute calibration for all JWST instruments. We describe in detail the steps necessary to measure IRAC photometry from archive retrieval to photometric corrections. To validate our photometry, we examine the distribution of uncertainties from all detections in all four IRAC channels as well as compare the photometry and its uncertainties to those from models, ALLWISE, and the literature. Seventy-five percent of our detections have standard deviations per star of all observations within each channel of less than 3%. The median standard deviations are 1.2%, 1.3%, 1.1%, and 1.9% in [3.6]-[8.0], respectively. We find less than 8% standard deviations in differences of our photometry with ALLWISE and excellent agreement with literature values (less than 3% difference), lending credence to our measured fluxes. JWST is poised to do groundbreaking science, and accurate calibration and cross-calibration with other missions will be part of the underpinnings of that science.

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IPAC Authors
(alphabetical)

Sean Carey

Senior Scientist


Grillmaira

Carl Grillmair

Associate Scientist


Jim Ingalls

Associate Scientist


Jessica_krick

Jessica Krick

Associate Scientist


Seppo_laine

Seppo Laine

Associate Scientist


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Patrick Lowrance

Senior Scientist


Schuyler Van Dyk

Senior Scientist