A MULTI-WAVELENGTH VIEW OF THE STAR FORMATION ACTIVITY AT z ∼ 3

We present a multi-wavelength, UV-to-radio analysis for a sample of massive (M* ∼ 1010 M☉) IRAC- and MIPS 24 μm detected Lyman break galaxies (LBGs) with spectroscopic redshifts z ∼ 3 in the GOODS-North field. For LBGs without individual 24 μm detections, we employ stacking techniques at 24 μm, 1.1 mm, and 1.4 GHz to construct the average UV-to-radio spectral energy distribution and find it to be consistent with that of a luminous infrared galaxy with LIR = 4.5+1.1−2.3 × 1011 L☉ and a specific star formation rate of 4.3 Gyr−1 that corresponds to a mass doubling time ∼230 Myr. On the other hand, when considering the 24 μm detected LBGs we find among them galaxies with LIR>1012 L☉, indicating that the space density of z ∼ 3 UV-selected ultra-luminous infrared galaxies (ULIRGs) is ∼(1.5 ± 0.5) × 10−5 Mpc−3. We compare measurements of star formation rates from data at different wavelengths and find that there is tight correlation (Kendall's τ>99.7%) and excellent agreement between the values derived from dust-corrected UV, mid-IR, millimeter, and radio data for the whole range of LIR up to LIR ∼ 1013 L☉. This range is greater than that for which the correlation is known to hold at z ∼ 2, possibly due to the lack of significant contribution from polycyclic aromatic hydrocarbons to the 24 μm flux at z ∼ 3. The fact that this agreement is observed for galaxies with LIR>1012 L☉ suggests that star formation in UV-selected ULIRGs, as well as the bulk of star formation activity at this redshift, is not embedded in optically thick regions as seen in local ULIRGs and submillimeter-selected galaxies at z = 2.