Cake Talk by Hiddo Algera from Hiroshima University/NAOJ
In recent years, a large number of massive galaxies have been discovered within the first Gyr after the Big Bang, raising the question of how so much mass was assembled in such a short time. In particular, some of these galaxies are dust-rich, suggesting that dust is also being produced in a rapid manner in the early Universe. In this talk, I will discuss our knowledge of dust in the epoch of reionization from an observational perspective, with a particular focus on the recently carried out Cycle 7 ALMA Large Program REBELS. REBELS constitutes a systematic survey of the dust contents and ISM of z~7 galaxies, and has increased the number of known dusty galaxies at this epoch by a factor of three. I will first present an outline of the REBELS program, followed by a discussion of recent results from its large number of dust continuum detections, including 1) the typical fraction of obscured star formation in UV-selected galaxies at z~7, and 2) new constraints on the dust-obscured cosmic star formation rate density in the epoch of reionization. In addition, I will discuss multi-band ALMA follow-up observations of z~7 dusty galaxies, and use these to constrain their dust temperatures and masses. Finally, I will discuss the accurate measurement of the dust emissivity index in a normal star-forming galaxy at z=7.3, providing insight into the physical properties of dust grains in the early Universe.