Spitzer IRAC observations of JWST calibration stars

TL;DR

This paper provides detailed infrared photometry of 36 potential JWST calibration stars using archival Spitzer IRAC data, validating the measurements against models and other surveys to support JWST's calibration needs.

Contribution

It offers a comprehensive methodology for extracting and correcting IRAC photometry from archives, enhancing calibration accuracy for JWST instruments.

Findings

75% of detections have <3% standard deviation in all channels

Photometry agrees within 8% with ALLWISE data

Flux measurements are consistent with literature values

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 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. 75% of our detections have standard deviations per star of all observations within each channel of less than three percent. 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 ground-breaking science, and accurate calibration and cross-calibration with other missions will be part of the underpinnings of that science.