Abstract
The Atacama Large Millimetre/submillimetre Array (ALMA) is currently in the process of transforming our view of star-forming galaxies in the distant () universe. Before ALMA, most of what we knew about dust-obscured star formation in distant galaxies was limited to the brightest submillimetre sources—the so-called submillimetre galaxies (SMGs)—and even the information on those sources was sparse, with resolved (i.e. sub-galactic) observations of the obscured star formation and gas reservoirs typically restricted to the most extreme and/or strongly lensed sources. Starting with the beginning of early science operations in 2011, the last 9 years of ALMA observations have ushered in a new era for studies of high-redshift star formation. With its long baselines, ALMA has allowed observations of distant dust-obscured star formation with angular resolutions comparable to—or even far surpassing—the best current optical telescopes. With its bandwidth and frequency coverage, it has provided an unprecedented look at the associated molecular and atomic gas in these distant galaxies through targeted follow-up and serendipitous detections/blind line scans. Finally, with its leap in sensitivity compared to previous (sub-)millimetre arrays, it has enabled the detection of these powerful dust/gas tracers much further down the luminosity function through both statistical studies of colour/mass-selected galaxy populations and dedicated deep fields. We review the main advances ALMA has helped bring about in our understanding of the dust and gas properties of high-redshift () star-forming galaxies during these first 9 years of its science operations, and we highlight the interesting questions that may be answered by ALMA in the years to come.
Highlights
Thanks to the pioneering observations of the extragalactic background light (EBL) since the 1980s and 1990s by early infrared satellites like the Infrared Astronomical Satellite (IRAS) and the Cosmic Background Explorer (COBE), it is well known that the cosmic infrared background (CIB) has an intensity similar to the optical background, implying that there is a comparable amount of light absorbed by dust and reradiated in the FIR as there is observable directly in the UV/optical [86,87]; see Cooray [88] for a recent review
Note that Rujopakarn et al [428] do not find any evidence for a size difference between the ALMA and Very Large Array (VLA) sizes of their FIR-fainter sources, consistent with the agreement they reported between the FIR continuum and rest-frame optical/UV sizes
The leap in sensitivity and angular resolution enabled by ALMA means that we can carry out the deepest continuum observations ever achieved atmillimetre wavelengths, and attempt to detect dust emission in low-mass, optical/near-IR-selected galaxies that are thought to be the dominant contributors to the cosmic SFR density at z > 5, notably Lyman-break galaxies (LBGs; e.g. [522,523])
Summary
When newly formed stars and their surrounding HII regions exist in the presence of cosmic dust grains, a fraction of the short-wavelength emission may be absorbed by those grains and re-emitted in the far-infrared (FIR). Jansky Very Large Array (VLA [18,19]), single-dish submillimetre telescopes such as the James Clerk Maxwell Telescope (JCMT; [20]), the IRAM 30-metre telescope [21], the Atacama Submillimetre Telescope Experiment (ASTE; [22]), the Atacama Pathfinder EXperiment (APEX; [23]), and the South Pole Telescope (SPT; [24]), and earlier (sub-)millimetre interferometers such as the Submillimetre Array (SMA; [25]) and the Plateau de Bure interferometer (PdBI; [26] succeeded by the NOrthern Extended Millimetre Array, NOEMA) These facilities have already revolutionized our view of high-redshift dusty star formation, from discovering submillimetre galaxies (SMGs) in the first extragalactic surveys with single-dish submillimetre telescopes, to quantifying the relative contribution of dusty star formation over much of cosmic time. All of these pre-ALMA-era limitations meant that the nature of dust-obscured star formation at highredshift—including the morphology, associated gas content, dynamics, efficiency, obscured fraction, contribution to the infrared background, or even what sources host it—remained largely unknown
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