THE IMPACT OF JWST BROADBAND FILTER CHOICE ON PHOTOMETRIC REDSHIFT ESTIMATION

Abstract

The determination of galaxy redshifts in the James Webb Space Telescope ’s ( JWST ) blank-field surveys will mostly rely on photometric estimates, based on the data provided by JWST ’ s Near-Infrared Camera (NIRCam) at 0.6–5.0 μ m and Mid Infrared Instrument (MIRI) at . In this work we analyze the impact of choosing different combinations of NIRCam and MIRI broadband filters (F070W to F770W), as well as having ancillary data at , on the derived photometric redshifts ( z phot ) of a total of 5921 real and simulated galaxies, with known input redshifts z  = 0–10. We found that observations at are necessary to control the contamination of high- z samples by low- z interlopers. Adding MIRI (F560W and F770W) photometry to the NIRCam data mitigates the absence of ancillary observations at and improves the redshift estimation. At z  = 7–10, accurate z phot can be obtained with the NIRCam broadbands alone when , but the z phot quality significantly degrades at . Adding MIRI photometry with 1 mag brighter depth than the NIRCam depth allows for a redshift recovery of 83%–99%, depending on spectral energy distribution type, and its effect is particularly noteworthy for galaxies with nebular emission. The vast majority of NIRCam galaxies with [F150W] = 29 AB mag at z  = 7–10 will be detected with MIRI at [F560W, F770W] mag if these sources are at least mildly evolved or have spectra with emission lines boosting the mid-infrared fluxes.