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2019 Fiscal Year Final Research Report

The physical origin of active galactic nucleus torus probed by high resolution mm/submm emission lines

Research Project

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Project/Area Number 17K14247
Research Category

Grant-in-Aid for Young Scientists (B)

Allocation TypeMulti-year Fund
Research Field Astronomy
Research InstitutionNational Astronomical Observatory of Japan

Principal Investigator

IZUMI TAKUMA  国立天文台, ハワイ観測所, 特任助教 (40792932)

Project Period (FY) 2017-04-01 – 2020-03-31
Keywords活動銀河核 / AGN / トーラス / サブミリ波 / ALMA / 輻射駆動噴水モデル / ガス輝線
Outline of Final Research Achievements

Active galactic nucleus (AGN) is an actively mass-accreting super massive black hole at the heart of galaxies. It has been long thought that there is a donut-like dusty/gaseous structure around an AGN, which is called as "AGN torus": this is a key structure to discuss AGN physical properties and its cosmological evolution. However, since the advent of the torus paradigm, its physical origin has been unclear for 30 yrs. In this study, we considered a new model for the origin of the torus, namely "radiation-driven fountain torus model", in which multi-phase gas dynamics driven by the AGN radiation naturally forms a geometrically thick donut-like structure. We tested this model by high resolution submm molecular and atomic gas observations with ALMA. We successfully obtained very consistent results to the model predictions, which surely supports the validity of this fountain model as the physical origin of the torus, a long-lasting mystery of modern astronomy.

Free Research Field

天文学

Academic Significance and Societal Importance of the Research Achievements

活動銀河核トーラスは、宇宙の古今にわたる活動銀河核、すなわち超巨大ブラックホールの周辺構造の中でも根幹をなす重要構造である。その一方で、提唱から30年以上にわたってその物理的な形成過程は不明なままで、いわゆる「ドーナツ型」モデルが便宜的に利用されてきた。本研究では、そのトーラスの物理的起源を「輻射駆動されたガスの噴水構造」にあるとし、ALMAを用いた最新の高解像度観測からその検証を行なった。観測結果は理論予測と非常によく整合しており、輻射駆動噴水モデルの妥当性を示している。これにより、トーラスは決して静的な構造ではなく、多相ガスが織りなす非常にダイナミックな構造であることが明らかとなった。

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Published: 2021-02-19  

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