Lyman-break galaxies (LBGs) represent one of the kinds of star-forming galaxies that are found in the high-redshift universe. The detection of LBGs in the far-infrared (FIR) domain can provide very important clues on their dust attenuation and total star-formation rate (SFR), allowing a more detailed study than has been performed so far. In this work we explore the FIR emission of a sample of 16 LBGs at z ∼ 3 in the GOODS-North and GOODS-South fields that are individually detected in PACS-100 μm or PACS-160 μm. These detections demonstrate the possibility of measuring the dust emission of LBGs at high redshift. We find that PACS-detected LBGs at z ∼ 3 are highly obscured galaxies which belong to the ultra-luminous or hyper-luminous IR galaxy class. Their total SFR cannot be recovered with the dust attenuation factors obtained from their UV continuum slope or their SED-derived dust attenuation employing Bruzual & Charlot (2003) templates. Both methods underestimate the results for most of the galaxies. Comparing with a sample of PACS-detected LBGs at z ∼ 1, we find evidence that the FIR emission of LBGs might have changed with redshift, in the sense that the dustiest LBGs found at z ∼ 3 have more prominent FIR emission, are dustier for a given UV slope, and have higher SFR for a given stellar mass than the dustiest LBGs found at z ∼ 1.

We study the star-forming (SF) population of galaxies within a sample of 209 IR-selected galaxy clusters at 0.3 ≤ z ≤ 1.1 in the ELAIS-N1 and XMM-LSS fields, exploiting the first HSC-SSP data release. The large area and depth of these data allows us to analyze the dependence of the SF fraction, f SF , on stellar mass and environment separately. Using R/R 200 to trace environment, we observe a decrease in f SF from the field towards the cluster core, which strongly depends on stellar mass and redshift. The data show an accelerated growth of the quiescent population within the cluster environment: the f SF vs. stellar mass relation of the cluster core (R/R 200 ≤ 0.4) is always below that of the field (4 ≤ R/R 200 < 6). Finally, we find that environmental and mass quenching efficiencies depend on galaxy stellar mass and distance to the center of the cluster, demonstrating that the two effects are not separable in the cluster environment. We suggest that the increase of the mass quenching efficiency in the cluster core may emerge from an initial population of galaxies formed "in situ." The dependence of the environmental quenching efficiency on stellar mass favors models in which galaxies exhaust their reservoir of gas through star formation and outflows, after new gas supply is truncated when galaxies enter the cluster.

We describe a new Large Program in progress on the Gemini North and South telescopes: Gemini Observations of Galaxies in Rich Early Environments (GOGREEN). This is an imaging and deep spectroscopic survey of 21 galaxy systems at 1 < z < 1.5, selected to span a factor >10 in halo mass. The scientific objectives include measuring the role of environment in the evolution of low-mass galaxies, and measuring the dynamics and stellar contents of their host haloes. The targets are selected from the SpARCS, SPT, COSMOS, and SXDS surveys, to be the evolutionary counterparts of today's clusters and groups. The new red-sensitive Hamamatsu detectors on GMOS, coupled with the nod-and-shuffle sky subtraction, allow simultaneous wavelength coverage over λ ∼ 0.6-1.05 µm, and this enables a homogeneous and statistically complete redshift survey of galaxies of all types. The spectroscopic sample targets galaxies with AB magnitudes z < 24.25 and [3.6] µm < 22.5, and is therefore statistically complete for stellar masses M * 10 10.3 M , for all galaxy types and over the entire redshift range. Deep, multiwavelength imaging has been acquired over larger fields for most systems, spanning u through K, in addition to deep IRAC imaging at 3.6 µm. The spectroscopy is ∼50 per cent complete as of semester 17A, and we anticipate a final sample of ∼500 new cluster members. Combined with existing spectroscopy on the brighter galaxies from GCLASS, SPT, and other sources, GOGREEN will be a large legacy cluster and field galaxy sample at this redshift that spectroscopically covers a wide range in stellar mass, halo mass, and clustercentric radius.