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Abstract The Atacama Large Millimeter/submillimeter Array (ALMA) Spectroscopic Survey in the Hubble Ultra Deep Field (ASPECS) Band 6 scan (212–272 GHz) covers potential [C ii ] emission in galaxies at 6 ≤ z ≤ 8 throughout a 2.9 arcmin 2 area. By selecting on known Ly α emitters (LAEs) and photometric dropout galaxies in the field, we perform targeted searches down to a 5 σ [C ii ] luminosity depth L [C II ] ∼ 2.0 × 10 8 L ⊙ , corresponding roughly to star formation rates (SFRs) of 10–20 M ⊙ yr −1 when applying a locally calibrated conversion for star-forming galaxies, yielding zero detections. While the majority of galaxies in this sample are characterized by lower SFRs, the resulting upper limits on [C ii ] luminosity in these sources are consistent with the current literature sample of targeted ALMA observations of z = 6–7 LAEs and Lyman-break galaxies (LBGs), as well as the locally calibrated relations between L [C ii ] and SFR—with the exception of a single [C ii ]-deficient, UV-luminous LBG. We also perform a blind search for [C ii ]-bright galaxies that may have been missed by optical selections, resulting in an upper limit on the cumulative number density of [C ii ] sources with L [C II ] > 2.0 × 10 8 L ⊙ (5 σ ) to be less than 1.8 × 10 −4 Mpc −3 (90% confidence level). At this luminosity depth and volume coverage, we present an observed evolution of the [C ii ] luminosity function from z = 6–8 to z ∼ 0 by comparing the ASPECS measurement to literature results at lower redshift. 

Abstract We make use of sensitive (9.3 μ Jy beam −1 rms) 1.2 mm continuum observations from the Atacama Large Millimeter/submillimeter Array (ALMA) Spectroscopic Survey in the Hubble Ultra-Deep Field (ASPECS) large program to probe dust-enshrouded star formation from 1362 Lyman-break galaxies spanning the redshift range z  = 1.5–10 (to ∼7–28 M ⊙ yr −1 at 4 σ over the entire range). We find that the fraction of ALMA-detected galaxies in our z  = 1.5–10 samples increases steeply with stellar mass, with the detection fraction rising from 0% at 10 9.0 M ⊙ to % at >10 10 M ⊙ . Moreover, on stacking all 1253 low-mass (<10 9.25 M ⊙ ) galaxies over the ASPECS footprint, we find a mean continuum flux of −0.1 ± 0.4 μ Jy beam −1 , implying a hard upper limit on the obscured star formation rate of <0.6 M ⊙ yr −1 (4 σ ) in a typical low-mass galaxy. The correlation between the infrared excess (IRX) of UV-selected galaxies ( L IR / L UV ) and the UV-continuum slope is also seen in our ASPECS data and shows consistency with a Calzetti-like relation at > and an SMC-like relation at lower masses. Using stellar mass and β measurements for z  ∼ 2 galaxies over the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey, we derive a new empirical relation between β and stellar mass and then use this correlation to show that our IRX– β and IRX–stellar mass relations are consistent with each other. We then use these constraints to express the IRX as a bivariate function of β and stellar mass. Finally, we present updated estimates of star formation rate density determinations at z  > 3, leveraging present improvements in the measured IRX and recent probes of ultraluminous far-IR galaxies at z  > 2.