The dust properties of star-forming galaxies in the first billion years

TL;DR

Recent ALMA observations of early galaxies in the first billion years reveal significant dust presence with unique properties, uncovering new populations and spatial emission offsets, advancing understanding of galaxy formation in the epoch of reionization.

Contribution

This review highlights new findings from ALMA's deep observations of high-redshift galaxies, including dust detection, properties, and unexpected populations, advancing knowledge of early galaxy evolution.

Findings

Detection of significant dust in galaxies at z~7

Identification of a new population of dust-obscured galaxies

Discovery of spatial offsets between UV and infrared emission

Abstract

The Atacama Large Millimetre/Sub-millimetre Array (ALMA) is obtaining the deepest observations of early galaxies ever achieved at (sub-)millimetre wavelengths, and detecting the dust emission of young galaxies in the first billion years of cosmic history, well in the epoch of reionization. Here I review some of the latest results from these observations, with special focus on the REBELS large programme, which targets a sample of 40 star-forming galaxies at z~7. ALMA detects significant amounts of dust in very young galaxies, and this dust might have different properties to dust in lower-redshift galaxies. I describe the evidence for this, and discuss theoretical/modelling efforts to explain the dust properties of these young galaxies. Finally, I describe two additional surprising results to come out of the REBELS survey: (i) a new population of completely dust-obscured galaxies at z~7, and (ii) the prevalence of spatial offsets between the ultraviolet and infrared emission of UV-bright, high-redshift star-forming galaxies.