SPT-SMGs: Half of the energy produced since recombination has been absorbed and reemitted by dust. This radiation, the cosmic infrared background (CIB), is produced primarily by dusty, star-forming galaxies (DSFGs) at z~1-3, with a tail extending beyond z>6. These objects were first identified in submillimeter-wavelength (submm) surveys of the extragalactic sky and found to be orders of magnitude more abundant in the early Universe than the present day. These studies upended our view of cosmic star formation, demonstrating that the bulk of star formation activity in the Universe could be taking place in DSFGs that were invisible in optical and ultraviolet surveys due to dust obscuration.

The South Pole Telescope's (SPT) SZ survey has systematically identified a large number of high-redshift strongly gravitationally lensed starburst galaxies in a cosmological survey of the millimeter (mm) sky. These sources are selected by their extreme mm flux, which is largely independent of redshift and lensing configuration. Due to the strong gravitational lensing, these objects typically appear an order of magnitude more luminous than the bulk DSFG population, with a corresponding increase in their solid angle on the sky. This magnification provides a reduction in the integration times required to detect lensed sources, makes weak spectral lines accessible, and increases the resolving power of our telescopes.

Over the past decade, we conducted a spectroscopic redshift survey with the Atacama Large Millimeter Array (ALMA) targeting 81 sources from the first-generation SPT survey. We obtained redshifts for the entire sample and determined that roughly half of these sources lie at z>4, indicating the fraction of dusty starburst galaxies at high redshift is far higher than previously thought. The highest-redshift source, SPT0311-58 at z=6.9, demonstrates that large reservoirs of molecular gas and dust can be present in massive galaxies near the end of the epoch of cosmic reionization. These sources were additionally targeted with high-resolution imaging with ALMA, unambiguously demonstrating that the targets are mostly strongly gravitationally lensed by foreground structure, and enabling us to make detailed and robust lens models. Around 10% of the targeted sources were found to be protocluster candidates.

Vieira et al. 2013, Nature; LA Times; Science Daily; Phys.Org; Universe Today; Space.com

Yordanka Apostolovski - Universidad de Valparaiso

Manuel Aravena - Universidad Andres Bello

Melanie Archipley - University of Chicago

Matthew Ashby - Harvard-Smithsonian Center for Astrophysics

Bradford Benson - University of Chicago

Matthieu Bethermin - Laboratoire d'Astrophysique de Marseille

Jack Birkin - Texas A&M University

Simon Birrer - Stony Brook University

Lindsey Bleem - Argonne National Laboratory

Rebecca Canning - University of Portsmouth

John Carlstrom - University of Chicago

Jared Cathey - University of Florida

Scott Chapman - University of British Columbia

Tom Crawford - University of Chicago

Roger Deane - University of Pretoria

Veronica Dike - University of Illinois, Urbana-Champaign

Frank Fu - University of Illinois, Urbana-Champaign

Anthony Gonzalez - University of Florida

Thomas Greve - Cosmic Dawn Center (DAWN) / DTU Space

Gayathri Gururajan - Scuola Internazionale Superiore Studi Avanzati (SISSA)

Chris Hayward - Flatiron CCA

Yashar Hezaveh - University of Montreal

Ryley Hill - University of British Columbia

Gil Holder - University of Illinois, Urbana-Champaign

Bill Holzapfel - University of California Berkeley

Sree Vani Jarugula - Fermilab

Seonwoo Kim - University of Illinois, Urbana-Champaign

Matt Malkan - University of California Los Angeles

Dan Marrone - University of Arizona

Karl Menten - Max Planck Institute

Eric Murphy - University of Virginia

Desika Narayanan - University of Florida

Sydnee O'Donnell - University of Illinois, Urbana-Champaign

Zhaodi Pan - Argonne National Laboratory

Kedar Phadke - University of Illinois, Urbana-Champaign

Ana Posses - Texas A&M University

Christian Reichardt - The University of Melbourne

Cassie Reuter - University of California Berkeley

Kaja Rotermund - Dalhousie University

Justin Spilker - Texas A&M University

Tony Stark - Harvard-Smithsonian Center for Astrophysics

Nikolaus Sulzenauer - Max Planck Institute

Mathilde Van Cuyck - University of Illinois, Urbana-Champaign

Joaquin Vieira - University of Illinois, Urbana-Champaign

David Vizgan - University of Illinois, Urbana-Champaign

Yujie Wan - University of Illinois, Urbana-Champaign

Axel Weiss - Max Planck Institute

Briana Wirag - Texas A&M University

Nan Zhang - University of Illinois, Urbana-Champaign

Dazhi Zhou - University of British Columbia