stellar spectra from @Pickles:1998 and synthetic stellar spectra from @Lejeune_etal:1997, convolved with the filter responses of the VLT instruments used in @Daddi_etal:2004. These derived colours provide a convenient reference for matching stars on the well-defined BzK stellar locus. We use the adjusted stellar locus of K06 in the following way.

The stellar locus can be split into a main branch and a “knee” feature, clearly visible in the lower part of figure \[bzk\]. The intersection of these branches provides a fixed point in the BzK plane from which we can derive a quantitative adjustment. Using a least squares fit to each section, we derived the following offset in $z-K$ and $B-z$ colours to this fixed point to convert to the photometric system of @Daddi_etal:2004: $$(z-K)_{Daddi} = (z^{\prime}-K)_{UDS} - 0.26$$ $$(B-z)_{Daddi} = (B-z^{\prime})_{UDS} + 0.06$$

This correction is then applied to all sources in the BzK plane. We henceforth refer to BzK photometry defined in this way.

The standard BzK definitions of @Daddi_etal:2004 were then used to construct our BzK sample. K-band sources ($> 5 \sigma$) from the UDS were used as the primary catalogue, with optical magnitudes extracted directly from the Subaru imaging data after careful matching of the Subaru 