The impact of JWST broad-band filter choice on photometric redshift estimation

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he 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 μm and Mid Infrared Instrument (MIRI) at λ > 5.0 μm . 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 λ < 0.6 μm , on the derived photometric redshifts (zphot) of a total of 5921 real and simulated galaxies, with known input redshifts z = 0–10. We found that observations at λ < 0.6 μm 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 λ < 0.6 μm and improves the redshift estimation. At z = 7–10, accurate z_(phot) can be obtained with the NIRCam broadbands alone when S/N ≥10, but the z_(phot) quality significantly degrades at S/N ≤ 5. 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] < 28 mag if these sources are at least mildly evolved or have spectra with emission lines boosting the mid-infrared fluxes.
© 2016. The American Astronomical Society. Artículo firmado por 11 autores. This work is partly based on observations taken with the NASA/ESA Hubble Space Telescope, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555; with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA; and with the Very Large Telescope, operated by the European Southern Observatory (ESO) at Cerro Paranal. L.B. and K.I.C. acknowledge the support of the Nederlandse Onderzoekschool voor de Astronomie (NOVA). K.I.C. also acknowledges funding from the European Research Council through the award of the Consolidator Grant ID 681627- BUILDUP. O.L.F. acknowledges funding from the European Research Council Advanced Grant ID 268107-EARLY. P.G. P.-G. acknowledges support from the Spanish Government MINECO Grants AYA2012-31277 and AYA2015-70815- ERC. L.G. acknowledges support from the Spanish Government MINECO Grants AAYA2012-32295. J.P. acknowledges the UK Science and Technology Facilities Council and the UK Space Agency for their support of the UK’s JWST MIRI development activities. We thank Macarena García-Marín, Alistair Glasse, and Álvaro Labiano for providing us the most updated versions of the JWST MIRI filter transmission curves. We also thank an anonymous referee for a careful and constructive report.
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