Authors

Abstract

We present and make publicly available accurate and precise photometric redshifts in the 2 deg2 COSMOS field for objects with iAB 23. The redshifts are computed using a combination of narrow band photometry from PAUS, a survey with 40 narrow bands spaced at 100 intervals covering the range from 4500 to 8500, and 26 broad, intermediate, and narrow bands covering the UV, visible and near infrared spectrum from the COSMOS2015 catalogue. We introduce a new method that models the spectral energy distributions (SEDs) as a linear combination of continuum and emission line templates and computes its Bayes evidence, integrating over the linear combinations. The correlation between the UV luminosity and the OII line is measured using the 66 available bands with the zCOSMOS spectroscopic sample, and used as a prior which constrains the relative flux between continuum and emission line templates. The flux ratios between the OII line and H, H and OIII are similarly measured and used to generate the emission line templates. Comparing to public spectroscopic surveys via the quantity z (zphotozspec)/(1+zspec), we find the photometric redshifts to be more precise than previous estimates, with 68(z ) (0.003, 0.009) for galaxies at magnitude iAB 18 and iAB 23, respectively, which is 3 and 1.66 tighter than COSMOS2015. Additionally, we find the redshifts to be very accurate on average, yielding a median of the z distribution compatible with |median(z )| 0.001 at all redshifts and magnitudes considered. Both the added PAUS data and new methodology contribute significantly to the improved results. The catalogue produced with the technique presented here is expected to provide a robust redshift calibration for current and future lensing surveys, and allows one to probe galaxy formation physics in an unexplored luminosity-redshift regime, thanks to its combination of depth, completeness and excellent redshift precision and accuracy.