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Fig. 1


Comparison of COSMOS2015 photometric redshifts ([3.6] < 25.4) versussecure spectroscopic redshifts (see Sect. 2.1) from the zCOSMOS-bright, zCOSMOS-deep, and VUDS surveys. Stars and known AGNs are included in the comparison as their identity is not generally known a priori. A scale bar indicates the density of objects in each region of the phase space. Filled red diamonds denote VUDS zspec members of PCl J1001+0220. The σNMAD for the wholesample and for 4 < z < 5 along with the median offset (Δz = (zphotzspec)∕(1 + zspec)) and the percentage of catastrophic outliers (|zphotzspec|∕(1 + zspec) > 0.15) for the latter redshift range are shown in the main panel. Residuals are shown in the bottom panel. We note that the spectroscopic sample at z > 4 has a median [3.6] magnitude nearly one magnitude brighter (Δm = 0.85) than the zphot sample adopted in this study meaning that these values are likely lower limits. We note also that all known catastrophic outliers at these redshifts result from the SED fitting confusing the Lyman break for the Balmer break and not the reverse, thus resulting in what is likely a pure but incomplete sample at 4 < z < 5. At z < 2 the two zCOSMOS samples dominate over VUDS providing 96.0% of all secure spectroscopic redshifts. At 2 ≤ z ≤ 3 the combined zCOSMOS samples and the VUDS sample are roughly matched in number with ~2000 spectroscopic redshifts each. At higher redshifts, z > 3 and z > 4, the VUDS sample dominates providing 83.9% and 97.3% of the secure spectroscopic redshifts, respectively.

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