Black hole candidates display transitions between hard and soft X-ray states. During the transition, quasi-periodic oscillations and jet ejections are observed, and the black hole accretion flow shows intense activity. Our group has investigated the process of the formation of the soft X-ray emitting region by the cooling of the...
The Epoch of Reionization (EoR) shaped the properties of the baryonic content of the Universe. Using hydrodynamical and radiative-transfer numerical simulations, we investigate in detail the processes taking place in the IGM before, during and after the EoR. Present and future observations by, e.g., PAPER, LOFAR, SKA, and E-ELT, will...
This talk will highlight some progress made based on our efforts of computing the universe, in order to understand the dynamics of gas in the universe, from intergalactic to interstellar medium. Select observables presented include the cosmic web from redshift zero to z=2-4, and the escape fraction of Lyman continuum...
Dust coagulation in protoplanetary disks is the first step of planetesimal formation. However, a pathway from dust aggregates to planetesimals remains unclear. Both laboratory and numerical studies have so far shown that the structure of a dust aggregate plays important roles in planetesimal formation. However, the aggregate structure has been...
The formation of the first stars after the big bang is one of the most important outstanding problems in modern astrophysics. While recent theoretical studies of the formation of individual first stars revealed the importance of radiative feedback and led to estimates first star the masses of first stars, studies...
電波干渉系 ALMA の登場によって、宇宙再電離時代 (宇宙年齢がおそよ2-10億年) にある銀河の研究は新時代を拓いた。サブミリ波帯に赤方偏移した遠赤外の微細構造輝線 ([OIII] 88μm, [CII] 158μm など) を ALMA で観測することで、再電離時代の星形成銀河を分光同定することが可能になったのである (e.g., Inoue et al. 2016, Science)。さらに、このような宇宙初期の時代、既に豊富なダストが存在することも明らかになってきた (e.g., Watson et al. 2015, Nature)。 本発表では、私たちのグループが推進している超遠方銀河の微細構造輝線 (主に [OIII] 88 μm) およびダスト連続光の観測結果を紹介する。まず私たちは、重力レンズ効果によって明るく見えている遠方銀河１天体を観測した。この結果、赤方偏移 z = 9.11 (宇宙年齢 5.5億年) にある [OIII] 88 μm の分光検出に成功した (Hashimoto et al. 2018a, Nature)。これは現在最も遠い輝線天体である。さらに、ハッブル宇宙望遠鏡やスピッツァー宇宙望遠鏡のデータも組み合わせた多波長データ解析から、観測時点よりも過去の星形成の歴史を遡った。この結果、この銀河が星形成を開始したのは z ~ 15 (宇宙年齢2.5億年) の頃だと推定され、宇宙最初期の星形成に知見を得た。次に、z...
Narrow Line Seyfert 1s (NLS1) are the lowest mass, highest mass accretion rate Active Galactic Nuclei (AGN) in the local Universe, with black hole masses of 1-10 million x Msun, accreting at the Eddington limit or beyond. These properties are similar to those expected for the majority of the first...
Self-gravitation can play a role in protoplanetary- and AGN-disks. If they are massive enough, gravitoturbulence sets in and acts as a strong driver for angular momentum redistribution. Thereby it moves large amounts of gas from the outer parts of the disk to the central object. However, if the disk cools...
Black hole candidates display transitions between hard and soft X-ray states. During the transition, quasi-periodic oscillations and jet ejections are observed, and the black hole accretion flow shows intense activity. Our group has investigated the process of the formation of the soft X-ray emitting region by the cooling of the...
December 2022 13 : 30 accretion discs, AGN, and MHD
The Epoch of Reionization (EoR) shaped the properties of the baryonic content of the Universe. Using hydrodynamical and radiative-transfer numerical simulations, we investigate in detail the processes taking place in the IGM before, during and after the EoR. Present and future observations by, e.g., PAPER, LOFAR, SKA, and E-ELT, will...
July 2022 13 : 30 reionization, high-z galaxies, and IGM
This talk will highlight some progress made based on our efforts of computing the universe, in order to understand the dynamics of gas in the universe, from intergalactic to interstellar medium. Select observables presented include the cosmic web from redshift zero to z=2-4, and the escape fraction of Lyman continuum...
June 2019 13 : 30 computational fluid dynamics, galaxy evolution, and cosmological simulations
Dust coagulation in protoplanetary disks is the first step of planetesimal formation. However, a pathway from dust aggregates to planetesimals remains unclear. Both laboratory and numerical studies have so far shown that the structure of a dust aggregate plays important roles in planetesimal formation. However, the aggregate structure has been...
May 2019 13 : 30 dust and protoplanetary discs
The formation of the first stars after the big bang is one of the most important outstanding problems in modern astrophysics. While recent theoretical studies of the formation of individual first stars revealed the importance of radiative feedback and led to estimates first star the masses of first stars, studies...
February 2019 15 : 15 numerical simulations, radiative transfer, and first stars
電波干渉系 ALMA の登場によって、宇宙再電離時代 (宇宙年齢がおそよ2-10億年) にある銀河の研究は新時代を拓いた。サブミリ波帯に赤方偏移した遠赤外の微細構造輝線 ([OIII] 88μm, [CII] 158μm など) を ALMA で観測することで、再電離時代の星形成銀河を分光同定することが可能になったのである (e.g., Inoue et al. 2016, Science)。さらに、このような宇宙初期の時代、既に豊富なダストが存在することも明らかになってきた (e.g., Watson et al. 2015, Nature)。 本発表では、私たちのグループが推進している超遠方銀河の微細構造輝線 (主に [OIII] 88 μm) およびダスト連続光の観測結果を紹介する。まず私たちは、重力レンズ効果によって明るく見えている遠方銀河１天体を観測した。この結果、赤方偏移 z = 9.11 (宇宙年齢 5.5億年) にある [OIII] 88 μm の分光検出に成功した (Hashimoto et al. 2018a, Nature)。これは現在最も遠い輝線天体である。さらに、ハッブル宇宙望遠鏡やスピッツァー宇宙望遠鏡のデータも組み合わせた多波長データ解析から、観測時点よりも過去の星形成の歴史を遡った。この結果、この銀河が星形成を開始したのは z ~ 15 (宇宙年齢2.5億年) の頃だと推定され、宇宙最初期の星形成に知見を得た。次に、z...
October 2018 13 : 30 reionization, ALMA, first galaxies, and first stars
Narrow Line Seyfert 1s (NLS1) are the lowest mass, highest mass accretion rate Active Galactic Nuclei (AGN) in the local Universe, with black hole masses of 1-10 million x Msun, accreting at the Eddington limit or beyond. These properties are similar to those expected for the majority of the first...
September 2018 13 : 30 seyfert galaxies, NLS1, AGN, and black holes
Self-gravitation can play a role in protoplanetary- and AGN-disks. If they are massive enough, gravitoturbulence sets in and acts as a strong driver for angular momentum redistribution. Thereby it moves large amounts of gas from the outer parts of the disk to the central object. However, if the disk cools...
August 2018 13 : 30 accretion discs, computational fluid dynamics, and numerical simulations
和 英