Key points are not available for this paper at this time.
A simple two color selection based on B-, z-, and K- band photometry is proposed for culling galaxies at 1. 4 -0. 2 (AB) allows to select actively star-forming galaxies at z>1. 4, independently on their dust reddening. Instead, objects with BzK 2. 5 (AB) colors include passively evolving galaxies at z>1. 4, often with spheroidal morphologies. Simple recipes to estimate the reddening, SFRs and masses of BzK-selected galaxies are derived, and calibrated on K<20 galaxies. Based on their UV (reddening-corrected), X-ray and radio luminosities, the BzK-selected star-forming galaxies with K<20 turn out to have average SFR ~ 200 Msun yr^-1, and median reddening E (B-V) ~0. 4. Besides missing the passively evolving galaxies, the UV selection appears to miss some relevant fraction of the z~2 star-forming galaxies with K<20, and hence of the (obscured) star-formation rate density at this redshift. The high SFRs and masses add to other existing evidence that these z=2 star-forming galaxies may be among the precursors of z=0 early-type galaxies. Theoretical models cannot reproduce simultaneously the space density of both passively evolving and highly star-forming galaxies at z=2. In view of Spitzer Space Telescope observations, an analogous technique based on the RJL photometry is proposed to complement the BzK selection and to identify massive galaxies at 2. 5
Daddi et al. (Sat,) studied this question.