We present a 0.72 deg2 contiguous 1.1‐mm survey in the central area of the Cosmological Evolution Survey field carried out to a 1σ≈ 1.26 mJy beam−1 depth with the AzTEC camera mounted on the 10‐m Atacama Submillimeter Telescope Experiment. We have uncovered 189 candidate sources at a signal‐to‐noise ratio (S/N) ≥ 3.5, out of which 129, with S/N ≥ 4, can be considered to have little chance of being spurious (≲2 per cent). We present the number counts derived with this survey, which show a significant excess of sources when compared to the number counts derived from the ∼0.5 deg2 area sampled at similar depths in the Submillimetre Common‐User Bolometer Array (SCUBA) HAlf Degree Extragalactic Survey (SHADES). They are, however, consistent with those derived from fields that were considered too small to characterize the overall blank‐field population. We identify differences to be more significant in the S1.1mm≳ 5 mJy regime, and demonstrate that these excesses in number counts are related to the areas where galaxies at redshifts z≲ 1.1 are more densely clustered. The positions of optical–infrared galaxies in the redshift interval 0.6 ≲z≲ 0.75 are the ones that show the strongest correlation with the positions of the 1.1‐mm bright population (S1.1mm≳ 5 mJy), a result which does not depend exclusively on the presence of rich clusters within the survey sampled area. The most likely explanation for the observed excess in number counts at 1.1‐mm is galaxy–galaxy and galaxy–group lensing at moderate amplification levels, which increases in amplitude as one samples larger and larger flux densities. This effect should also be detectable in other high‐redshift populations.

We present constraints on the dust continuum flux and inferred gas content of a gravitationally lensed massive quiescent galaxy at z = 1.883 ± 0.001 using AzTEC 1.1 mm imaging with the Large Millimeter Telescope. MRG-S0851 appears to be a prototypical massive compact quiescent galaxy, but evidence suggests that it experienced a centrally concentrated rejuvenation event in the last 100 Myr. This galaxy is undetected in the AzTEC image but we calculate an upper limit on the millimeter flux and use this to estimate the H2 mass limit via an empirically calibrated relation that assumes a constant molecular-gas-to-dust ratio of 150. We constrain the 3σ upper limit of the H2 fraction from the dust continuum in MRG-S0851 to be . MRG-S0851 has a low gas fraction limit with a moderately low sSFR owing to the recent rejuvenation episode, which together result in a relatively short depletion time of <0.6 Gyr if no further H2 gas is accreted. Empirical and analytical models both predict that we should have detected molecular gas in MRG-S0851, especially given the rejuvenation episode; this suggests that cold gas and/or dust is rapidly depleted in at least some early quiescent galaxies.

We present the first results from a confusion‐limited map of the Great Observatories Origins Deep Survey‐South (GOODS‐S) taken with the AzTEC camera on the Atacama Submillimeter Telescope Experiment. We imaged a field to a 1σ depth of 0.48–0.73  mJy beam−1, making this one of the deepest blank‐field surveys at mm‐wavelengths ever achieved. Although by traditional standards our GOODS‐S map is extremely confused due to a sea of faint underlying sources, we demonstrate through simulations that our source identification and number counts analyses are robust, and the techniques discussed in this paper are relevant for other deeply confused surveys. We find a total of 41 dusty starburst galaxies with signal‐to‐noise ratios S/N ≥ 3. 5 within this uniformly covered region, where only two are expected to be false detections, and an additional seven robust source candidates located in the noisier (1σ≈ 1  mJy beam−1) outer region of the map. We derive the 1.1  mm number counts from this field using two different methods: a fluctuation or “P(d)” analysis and a semi‐Bayesian technique and find that both methods give consistent results. Our data are well fit by a Schechter function model with . Given the depth of this survey, we put the first tight constraints on the 1.1  mm number counts at S1.1 mm= 0.5  mJy, and we find evidence that the faint end of the number counts at from various SCUBA surveys towards lensing clusters are biased high. In contrast to the 870 μm survey of this field with the LABOCA camera, we find no apparent underdensity of sources compared to previous surveys at 1.1 mm; the estimates of the number counts of SMGs at flux densities >1 mJy determined here are consistent with those measured from the AzTEC/SHADES survey. Additionally, we find a significant number of SMGs not identified in the LABOCA catalogue. We find that in contrast to observations at λ≤ 500 μm, MIPS 24 μm sources do not resolve the total energy density in the cosmic infrared background at 1.1  mm, demonstrating that a population of z≳ 3 dust‐obscured galaxies that are unaccounted for at these shorter wavelengths potentially contribute to a large fraction (∼2/3) of the infrared background at 1.1  mm.

Dusty star-forming galaxies (DSFGs) detected at z > 4 provide important examples of the first generations of massive galaxies. However, few examples with spectroscopic confirmation are currently known, with Hershel struggling to detect significant numbers of z > 6 DSFGs. NGP6 D1 is a bright 850 µm source (12.3 ± 2.5 mJy) with no counterparts at shorter wavelengths (a SPIRE dropout). Interferometric observations confirm it is a single source, with no evidence for any optical or NIR emission, or nearby likely foreground lensing sources. No > 3σ detected lines are seen in both LMT RSR and IRAM 30m EMIR spectra of NGP6 D1 across 32 GHz of bandwidth despite reaching detection limits of ∼ 1mJ y/500km s −1 , so the redshift remains unknown. Template fitting suggests that NGP6 D1 is most likely between z = 5.8 and 8.3. SED analysis finds that NGP6 D1 is a ULIRG, with a dust mass ∼ 10 8 -10 9 M and a SFR of ∼ 500 M yr −1 . We place upper limits on the gas mass of NGP6 D1 of M H2 < (1.1 ± 3.5) × 10 11 M , consistent with a gas-to-dust ratio of ∼ 100 -1000. We discuss the nature of NGP6 D1 in the context of the broader submm population, and find that comparable SPIRE dropouts account for ∼ 20% of all SCUBA-2 detected sources, but with a similar flux density distribution to the general population.

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