Tsukuba Uchu Forum

142nd Uchu Forum

ALMA and JWST exploration of high-redshift galaxies (and stars)

Yoshinobu Fudamoto

Chiba University

Extragalactic astronomy is currently in an exciting period. Observing high-redshift galaxies allows us to directly see galaxies in the distant past, dating back to when the Universe was only nearly a few hundred million years old. This remarkable feature has led astronomers to dedicate significant efforts toward finding and studying galaxies at high redshift to unravel the mysteries of galaxy formation and evolution in the early Universe. Particularly, over the past ten years of the Atacama Large Millimeter/submillimeter Array (ALMA) observations, combined with the recent breakthroughs from the James Webb Space Telescope (JWST), we have begun to access the extraordinarily detailed stellar and interstellar properties of galaxies at high redshift (e.g., z>4). These two extremely powerful telescopes have unprecedented capabilities that enable us to provide complementary information to understand galaxy formation and evolution by covering a wide range of different wavelengths. In particular, JWST efficiently captures emissions in rest-frame ultraviolet (UV)-to-optical wavelengths, shedding light on the ionized gas and stellar components of galaxies. In contrast, ALMA's rest-frame far-infrared (FIR) observations enable access to the "fuel" for star-formation activities: the neutral gas reservoirs of distant galaxies. Recent ALMA surveys of FIR emission lines have successfully provided us with statistically large enough samples of galaxies from z>4 to z>7 for the first time (e.g., ALPINE survey; Le Févre+20 and REBELS survey; Bouwens+21). In this talk, I will go through previous and ongoing observation efforts of ALMA across the redshift range of z~5 to z~9. I will then introduce several ongoing JWST observational efforts that have provided an extremely large amount of information. Finally, I will present an exciting example of recent time-domain extragalactic astronomy enabled by JWST. Such time-domain observations not only allow us to study galaxies in detail but also enable us to reach individual stellar properties within distant galaxies. Image