technique [@Daddi_etal:2004] which is based on $K$-band selection. Recent studies have shown that the BM/BX technique is reasonably efficient at selecting actively star-forming galaxies at $z\sim 2$, but largely misses the passive galaxy population at these epochs [@Quadri_etal:2007; @Grazian_etal:2007]. In contrast, the BzK method appears to be the most complete of the broad-band techniques for the selection of both star-forming and passive galaxies [@Daddi_etal:2004; @VanDokkum_etal:2006; @Grazian_etal:2007]. Based on initial $K$-band selection, in principle it does not suffer the same heavy biases caused by dust or the age of the stellar populations.

An alternative is to use a larger set of filters over a range of wavelengths and infer a galaxy’s redshift from comparison of the calculated magnitudes with a set of templates (@Cirasuolo_etal:2007 and references therein). This work makes use of such photometric redshifts and in principle one can derive the stellar age of a galaxy using such templates. However due to the uncertainties in determining stellar ages from the template fits, and the desire for comparison with the literature, the bulk of the present analysis is based on simple BzK selection.

The BzK technique was first developed using the K20 survey [@Cimatti_etal:2002] by [@Daddi_etal:2004], and preferentially selects star-forming and 