Quasar absorption systems as a probe of the galaxy and the circum galactic medium

2019 Fiscal Year Final Research Report

• Project/Area Number: 16K05299
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Astronomy
• Research Institution: Tokyo University of Science
• Principal Investigator: Okoshi Katsuya 東京理科大学, 基礎工学部教養(長万部), 准教授 (50453832)
• Project Period (FY): 2016-04-01 – 2020-03-31
• Keywords: クエーサー吸収線系 / 銀河形成 / 銀河間物質

Outline of Final Research Achievements

We have investigated an evolutionary relation between galaxy and the circum-galactic medium (CGM) through quasar absorption systems, Damped Lyman-alpha (DLA) absorption systems, which exhibit the highest HI column densities in the universe, and metal absorption systems. Our main results are as follows:
(1) At redshift z=1-2, the quasar absorption systems in the CGM show a strong correlation between the HI column densities and the low-ion column densities (e.g., MgII) with a scale within about 10 kpc. The multiple absorption systems indicate that the CGM extends up to a scale of about 500 kpc which is larger than the halo size of typical galaxy. (2) Our surveys for DLA galaxies on the Subaru/Keck observations put constraint on an upper limit of the star formation rates of 1 0 M(solar)/yr.
Further investigation based on statistically significant sample size is required by carrying out both radio and optical/infrared surveys for DLA galaxies.

Free Research Field

天文学

Academic Significance and Societal Importance of the Research Achievements

天文学では、我々の住む銀河系が、いつ誕生し、どのように進化をして現在の姿になっているかを解明することが重要な問いである。宇宙には、銀河系と似た銀河が数多く存在し、現代の大型望遠鏡によって、宇宙初期に遡って銀河の進化過程を詳細に観測できるようになった。本研究では、すばる望遠鏡などの大型望遠鏡を駆使して、原始銀河の周辺域ガスの物理的・化学的特性を調べることにより、銀河がどのように進化してきたのかという問いに対して有益な示唆を与えることができた。