Gas and dust in infrared galaxies and star formation mechanisms that determine cosmic evolution

2023 Fiscal Year Final Research Report

• Project/Area Number: 19K23462
• Research Category: Grant-in-Aid for Research Activity Start-up
• Allocation Type: Multi-year Fund
• Review Section: 0204:Astronomy, earth and planetary science, and related fields
• Research Institution: Hiroshima University
• Principal Investigator: Inami Hanae 広島大学, 宇宙科学センター, 助教 (20841943)
• Project Period (FY): 2019-08-30 – 2024-03-31
• Keywords: 銀河進化 / 銀河形成 / 赤外線銀河 / 星形成 / 星間ガス / 星間ダスト

Outline of Final Research Achievements

In this study, we used the ALMA observatory to investigate the gas and dust of infrared galaxies in the distant Universe. By comparing the mass and other characteristics of interstellar media with galaxy properties such as stellar masses, we were able to uncover the physical phenomena and mechanisms governing star formation in galaxies. In particular, our deep blind survey revealed molecular gas and dust in galaxies that existed around 10 billion years ago. We found that the cosmic molecular mass density in the Universe reached its peak around 10 billion years ago and declined as galaxies evolved toward the present Universe. Furthermore, by examining even earlier stages of the Universe, we verified the existence of galaxies from approximately 12 billion years ago through spectroscopic detections of carbon emission. Some of these galaxies also exhibited dust emission. These results suggest that massive galaxies and dust already existed shortly after the beginning of the Universe.

Free Research Field

天文学

Academic Significance and Societal Importance of the Research Achievements

本研究では星形成の原材料であるガスを約100億年前から現在の宇宙にある銀河について調査し、宇宙全体で平均的なガス質量密度は約100億年前にピークを持ち、現在の宇宙へ進化する過程で減少したことがわかった。これは星形成の進化と量的にほぼ一致しており、約100億年前に宇宙で多量の星が作られた主要因はガス質量が豊富であったからだと言える。また、約120億年前という宇宙の極初期でも大量のガスとガストをもつ銀河を発見し、宇宙誕生直後には既に大質量銀河が存在し、当初は想定されていなかった大量のダストが存在したことが分かった。