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2016.4.25-5.1

4月25日(月)13:30~15:00  太陽系小天体セミナー    南棟2階会議室
Apr 25 mon          Solar System Minor Body Seminar   Conference Room, South Bldg.2F

4月25日(月)13:30~14:30  臨時理論コロキウム    中央棟(北)1F講義室
Apr 25 mon          DTA special colloquium   Lecture Room, Central Building (North)

4月27日(水)10:30~12:00  総研大コロキウム 中央棟(北)1F講義室
Apr 27 wed          SOKENDAI colloquium   Lecture Room

4月27日(水)13:30~14:30  理論コロキウム コスモス会館会議室
Apr 27 wed           DTA colloquium   Conference Room, Cosmos Lodge

詳細は以下をご覧下さい。

4月25日(月)

キャンパス
三鷹
セミナー名
太陽系小天体セミナー
定例・臨時の別
定例
日時
4月25日(月曜日)13時30分~15時00分
場所
南棟2階会議室
講演者
大坪貴文

連絡先
 名前:渡部潤一
備考
テレビ会議またはスカイプによる参加も可

4月25日(月)

Campus
Mitaka
Seminar
DTA special colloquium (臨時理論コロキウム)
Regularly Scheduled/Sporadic
Sporadic
Date and time
25 April 2016, 13:30-14:30
Place
Lecture Room, Central Building (North)
Speaker
Kohei Inayoshi
Affiliation
Columbia University
Title
Hyper-Eddington accretion flows onto massive black holes
Abstract
How fast can black holes (BHs) grow? The existence of bright quasars at high-redshift provides a challenging puzzle about the origin of supermassive BHs. To form such massive objects within a billion year, rapid growth of seed BHs is required. We study very-high rate, spherically symmetric accretion flows onto massive BHs embedded in dense metal-poor clouds. We find solutions from outside the Bondi radius at hyper-Eddington rates, unimpeded by radiation feedback. Accretion rates in this regime are steady, and larger than 5000 L_Edd/c^2. At lower rates, the accretion is episodic due to radiative feedback and the average rate is below the Eddington rate. The hyper-Eddington accretion solution is maintained as long as the emergent luminosity is limited to < (10-30) L_Edd because of photon trapping due to electron scattering. We apply our result to the rapid formation of massive BHs in protogalaxies. Once a seed BH forms at the center of the galaxy, it can grow to a maximum ~ 10^5 Msun via gas accretion independent of the initial BH mass.
Facilitator
-Name:Tomoya Takiwaki
Comment
in English

4月27日(水)

Campus
Mitaka
Seminar Name : SOKENDAI colloquium
Regular / Irregular : Regular
Date:10:30-12:00,April 27,2016
Place
Lecture Room

Speaker 1:Kyoko Onishi

Affiliation
D3, SOKENDAI, Mitaka(supervisor : Satoru Iguchi)
Title
Molecular gas kinematics in the centres of galaxies
Speaker 2 : Koki Okutomi
Affiliation
SOKENDAI, Mitaka(supervisor : )
Title
TBD Organizer
Name : Kotomi Taniguchi
TV conference system is available connecting from Nobeyama, Hawaii,
Mizusawa, and Okayama.

4月27日(水)

Campus
Mitaka
Seminar
DTA colloquium
Regularly Scheduled/Sporadic
Regularly Scheduled Date and time:27 April 2016, 13:30-14:30
Place
Conference Room, Cosmos Lodge
Speaker
Tetsuo Taki
Affiliation
NAOJ CfCA
Title
Toward formation of rocky planetesimals: dust and gas density evolution at a local structure of protoplanetary disks
Abstract
The radial drift barrier is one of the most serious problem in the planetesimal formation process. We focus on a local disk structure called “radial pressure bump (Whipple, 1972; Haghighipour & Boss, 2003a, b)”. When a protoplanetary disk has the radial pressure bump, dust particles are trapped at a point where gas pressure is radially maximized. We investigate simultaneous evolution of dust and gas density profiles at a radial pressure bump. We find that the bump structure is flattened by a drag force from dust onto gas when the dust-to-gas mass ratio reaches ~1. Although the pressure bump is a favorable place for streaming instability (SI; Youdin & Goodman, 2005), the flattened bump structure inhibits SI from forming large particle clumps corresponding to 100-1000 km sized bodies, which has been previously proposed. If SI occurs there, the dust clumps formed would be 10-100 times smaller, that is, of about 1 – 100 km.
Facilitator
-Name:Tomoya Takiwaki
Comment
in English=

以上

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