2015ApJ...810...73C

We have analyzed a sample of 574 Spitzer 4.5 µm selected galaxies with and (AB) over the UltraVISTA ultradeep COSMOS field. Our aim is to investigate whether these mid-infrared (mid-IR) bright, near-infrared (near-IR) faint sources contribute significantly to the overall population of massive galaxies at redshifts. By performing a spectral energy distribution (SED) analysis using up to 30 photometric bands, we have determined that the redshift distribution of our sample peaks at redshifts-3.0, and of the galaxies lie at. We have studied the contribution of these sources to the galaxy stellar mass function (GSMF) at high redshifts. We found that the, galaxies produce a negligible change to the GSMF previously determined for sources at, but their contribution is more important at, accounting for of the galaxies with stellar masses. We also constrained the GSMF at the highest-mass end () at. From their presence at and virtual absence at higher redshifts, we can pinpoint quite precisely the moment of appearance of the first most massive galaxies as taking place in the Gyr of elapsed time between and. Alternatively, if very massive galaxies existed earlier in cosmic time, they should have been significantly dust-obscured to lie beyond the detection limits of current, large-area, deep near-IR surveys.