Free Astronomy Magazine January-February 2021

50 JANUARY-FEBRUARY 2021 ASTRO PUBLISHING But it was hard to say whether these discoveries were unique, or whether there were more galaxies like them out there. ALPINE is the first survey that enabled astronomers to study a significant num- ber of galaxies in the early universe, and it shows that they might evolve faster than expected. But the sci- entists don’t yet under- stand how these galaxies grew up so fast, and why some of them already have rotating disks. Observations from ALMA were crucial for this re- search because the radio telescope can see the star formation that is hidden by dust and trace the mo- tion of gas emitted from star-forming regions. Sur- veys of galaxies in the early universe commonly use optical and infrared telescopes. These allow the measurement of the unobscured star formation and stel- lar masses. However, these tele- scopes have difficulties measuring dust, obscured regions, where stars form, or the motions of gas in these galaxies. And sometimes they don’t something special about their envi- ronments,” added Paolo Cassata of the University of Padua in Italy, for- merly at the Universidad de Val- paraíso in Chile. ALPINE is the first and largest multi- wavelength survey of galaxies in the early universe. For a large sam- ple of galaxies the team collected measurements in the optical (in- cluding Subaru, VISTA, Hubble, Keck, and VLT), infrared (Spitzer), and radio (ALMA). Multi-wavelength studies are needed to get the full picture of how galax- ies are built up. “Such a large and complex survey is only possible thanks to the collaboration be- tween multiple institutes across the globe,” said Matthieu Béthermin of the Laboratoire d’Astrophysique de Marseille in France. see a galaxy at all. “With ALMA we discovered a few distant galaxies for the first time. We call these Hubble-dark as they could not be detected even with the Hubble tel- escope,” said Lin Yan of Caltech. To learn more about distant galaxies, the astronomers want to point ALMA at individual galaxies for a longer time. “We want to see ex- actly where the dust is and how the gas moves around. We also want to com- pare the dusty gal- axies to others at the same distance and figure out if there might be A short video explaining the result of the research. [B. Saxton NRAO/AUI/NSF] A rtist’s impression of what the MAMBO-9 galaxy would look like in visible light. The galaxy is very dusty and has yet to build most of its stars. [NRAO/AUI/NSF, B. Saxton] !