Absolute Flux Calibration of the IRAC Instrument on the Spitzer Space Telescope Using Hubble Space Telescope Flux Standards

May 2011 • 2011AJ....141..173B

Authors • Bohlin, R. C. • Gordon, K. D. • Rieke, G. H. • Ardila, D. • Carey, S. • Deustua, S. • Engelbracht, C. • Ferguson, H. C. • Flanagan, K. • Kalirai, J. • Meixner, M. • Noriega-Crespo, A. • Su, K. Y. L. • Tremblay, P. -E.

Abstract • The absolute flux calibration of the James Webb Space Telescope (JWST) will be based on a set of stars observed by the Hubble and Spitzer Space Telescopes. In order to cross-calibrate the two facilities, several A, G, and white dwarf stars are observed with both Spitzer and Hubble and are the prototypes for a set of JWST calibration standards. The flux calibration constants for the four Spitzer IRAC bands 1-4 are derived from these stars and are 2.3%, 1.9%, 2.0%, and 0.5% lower than the official cold-mission IRAC calibration of Reach et al., i.e., in agreement within their estimated errors of ~2%. The causes of these differences lie primarily in the IRAC data reduction and secondarily in the spectral energy distributions of our standard stars. The independent IRAC 8 μm band-4 fluxes of Rieke et al. are about 1.5% ± 2% higher than those of Reach et al. and are also in agreement with our 8 μm result.


IPAC Authors

Sean Carey

Senior Scientist