A Census of Optical and Near-Infrared Selected Star-forming and Passively Evolving Galaxies at Redshift z ~ 2

Using the extensive multiwavelength data in the GOODS-North field, including our ground-based rest-frame UV spectroscopy and near-IR imaging, we construct and draw comparisons between samples of optical and near-IR selected star-forming and passively evolving galaxies at redshifts 1.4 ≲ z ≲ 2.6. We find overlap at the 70%-80% level in samples of z ~ 2 star-forming galaxies selected by their optical (UnGℛ) and near-IR (BzK) colors when subjected to common K-band limits. Deep Chandra data indicate a ~25% AGN fraction among near-IR selected objects, much of which occurs among near-IR bright objects (Ks < 20; Vega). Using X-rays as a proxy for the bolometric star formation rate (SFR) and stacking the X-ray emission for the remaining (non-AGN) galaxies, we find that the SFR distributions of UnGℛ, BzK, and J - Ks > 2.3 galaxies (i.e., distant red galaxies; DRGs) are very similar as a function of Ks, with Ks < 20 galaxies having ⟨SFR⟩ ~ 120 M☉ yr-1, a factor of 2-3 higher than those with Ks > 20.5. The absence of X-ray emission from the reddest DRGs and BzK galaxies with (z - K)AB ≳ 3 indicates that they must have declining star formation histories to explain their red colors and low SFRs. While the M/L ratio of passively evolving galaxies may be larger on average, the Spitzer IRAC data indicate that their inferred stellar masses do not exceed the range spanned by optically selected galaxies, suggesting that the disparity in current SFR may not indicate a fundamental difference between optical and near-IR selected massive galaxies (M* > 1011 M☉). We consider the contribution of optical, near-IR, and submillimeter selected galaxies to the star formation rate density (SFRD) at z ~ 2, taking into account sample overlap. The SFRD in the interval 1.4 ≲ z ≲ 2.6 of UnGℛ and BzK galaxies to Ks = 22 and DRGs to Ks = 21 is ~0.10 ± 0.02 M☉ yr-1 Mpc-3. Optically selected galaxies to ℛ = 25.5 and Ks = 22.0 account for ~70% of this total. Greater than 80% of radio-selected submillimeter galaxies to S850 μm ~ 4 mJy with redshifts 1.4 < z < 2.6 satisfy either one or more of the BX/BM, BzK, and DRG criteria.