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Activity > Lunch Talk

Lunch Talk (2019)

ASIAA Lunch Talk is an institute-wide event allowing ASIAA researchers from different fields to discuss astronomy in a very casual manner. The informal meeting is usually held at lunch time on every Monday. Occasionally visitors are also invited to the lunch talk to share their research and ideas with ASIAA researchers.

    Contact
  • Lunch Talk: Colloquium Committee (talks_replace2@_asiaa.sinica.edu.tw)
  • Tech Lunch Talk: Huang, Yen-Ru (yenruhuang_replace2@_asiaa.sinica.edu.tw)
NEXT Lunch Talk: 2019-01-28 Mon 14:20~15:20 [R1203]
Speaker:Katharina Wollenberg
Topic:The Fragmentation Behavior of Population~III Protostellar Disks under the Influence of Turbulence and Rotation
Abstract:In cosmological simulations, it is found that the degree of fragmentation of the Population III (Pop III) protostellar disk varies strongly from halo to halo. This is to be expected if turbulence within the cloud plays a role in determining when and where fragmentation actually occurs. It is also reasonable to expect that the amount of angular momentum present at small-scales will have a large impact on Population III protostellar disk formation and evolution. We conducted a numerical study with the Voronoi moving-mesh AREPO in which we examined how different levels of initial subsonic turbulence and rotation within the star-forming cloud affect the outcome of Pop III star formation in terms of the total number of objects formed, the overall mass spectrum and the individual accretion history. We used controlled initial conditions which examine the collapse of a gas cloud with pre-defined levels of turbulence or rotation within a small computational box. This allowed us to draw conclusions on the specific role, strength and importance of the particular physical parameters applied here. In this talk, I will present some of our results and discuss the relevance of our numerical approach in which we have performed several realizations per combination of initial conditions and have averaged over the realizations instead of just considering single, individual runs.
No. Time/Place Speaker Topic (Abstract)
download PDF: dowaload talk PDF file
12019-04-22 Mon
12:15~13:15
R1203
Kevin Koay
[ASIAA]
22019-03-25 Mon
12:15~13:15
R1203
Miikka Väisälä
[ASIAA]
32019-03-18 Mon
12:15~13:15
R1203
Kouichi Hirotani
[ASIAA]
42019-03-11 Mon
12:15~13:15
R1203
Marco Muñoz-Gutierrez
[ASIAA]
52019-03-04 Mon
12:15~13:15
R1203
Shutaro Ueda
[ASIAA]
62019-02-25 Mon
12:15~13:15
R1203
Po-Sheng Ou
[NTU/ASIAA]
Modeling the Mass loss of Massive Stars with MESA
72019-02-18 Mon
12:15~13:15
R1203
Li-Hsin Chen
[NTU/ASIAA]
Simulations of the First Galaxies
82019-02-11 Mon
12:15~13:15
R1203
Yen-Chen Pan
[EACOA Fellow, NAOJ]
Host galaxies of Ia SNe
92019-01-28 Mon
14:20~15:20
R1203
Katharina Wollenberg
[ITA, Heidelberg]
The Fragmentation Behavior of Population~III Protostellar Disks under the Influence of Turbulence and Rotation
Abstract

In cosmological simulations, it is found that the degree of fragmentation of the Population III (Pop III) protostellar disk varies strongly from halo to halo. This is to be expected if turbulence within the cloud plays a role in determining when and where fragmentation actually occurs. It is also reasonable to expect that the amount of angular momentum present at small-scales will have a large impact on Population III protostellar disk formation and evolution. We conducted a numerical study with the Voronoi moving-mesh AREPO in which we examined how different levels of initial subsonic turbulence and rotation within the star-forming cloud affect the outcome of Pop III star formation in terms of the total number of objects formed, the overall mass spectrum and the individual accretion history. We used controlled initial conditions which examine the collapse of a gas cloud with pre-defined levels of turbulence or rotation within a small computational box. This allowed us to draw conclusions on the specific role, strength and importance of the particular physical parameters applied here. In this talk, I will present some of our results and discuss the relevance of our numerical approach in which we have performed several realizations per combination of initial conditions and have averaged over the realizations instead of just considering single, individual runs.

102019-01-21 Mon
12:15~13:15
R1203
Tzu-Hsiang Chao
[NTU/ASIAA]
Cosmological Impacts of the First Stars
112019-01-14 Mon
12:15~13:15
R1203
Sung-Han Tsai
[ASIAA/NCU]
Binary Stellar Evolution Models with MESA
122019-01-07 Mon
12:15~13:15
R1203
Tiara Hung/Edward Ashton
[UCSC/UBC]
Searching for Tidal Disruption Events in the Optical Time Domain (Hung) / Searching the OSSOS dataset for unusual objects: slow movers and interlopers (Ashton)
Abstract

Hung<br> Ashton: This talk combines two projects that uses the Outer Solar System Origins Survey (OSSOS) dataset to search for unusual small bodies. The first search looked for objects beyond 300 au using an uncommon search technique, we use an algorithm to identify objects that appear stationary on the timescale of hours but not present days/weeks/months before and after. After visually scanning all the candidates no slow moving objects were discovered. From the null detection and using a survey simulator, we obtain a model-dependent 95% upper limit of 1000 on the number of `planetary objects', with absolute magnitudes in the range -3 < H < 2, in the distant Solar System. In the second search we looked for interstellar objects (IS0s) using a slightly altered version of the TNO detection software used by OSSOS. No ISOs were discovered. However, we have found bound objects traveling at motions (when observed only over short arcs) that an ISO in the outer Solar System could have, and we show how previous moving-object surveys may have detected ISOs but incorrectly assigned them to bound orbits.

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