2017 Fiscal Year Research-status Report
The identification and distribution of warm dark matter subhalos
| Project/Area Number |
17K14271
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| Research Institution | The University of Tokyo |
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Principal Investigator |
Han Jiaxin 東京大学, カブリ数物連携宇宙研究機構, 特任研究員 (50791456)
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| Project Period (FY) |
2017-04-01 – 2020-03-31
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| Keywords | dark matter / subhalo / merger tree |
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| Outline of Annual Research Achievements |
The purpose of the research project was to develop a new method to find subhaloes in warm dark matter simulations and to model their distributions, based on modifications and extensions to the HBT algorithm. As a first step, in FY2017 we have developed a much improved version of the original HBT code, HBT+, which is much faster, more user friendly, and more complete in physics. We have also built a FoF halo finder into HBT+, in order to explore halo finding in warm dark matter simulations with varying linking length. We have applied HBT+ to the Millennium-II simulation and the Aquarius simulation, and have obtained much improved results in the halo merger-tree as well as the subhalo mass function. In particular, we have shown that HBT+ finds a more abundant population of massive subhaloes in the center of host haloes, and the spatial and mass distribution of these subhaloes deviate from the universal distribution for low mass ones, reflecting that the massive subhaloes are more resilient to tidal stripping. These results are in contrast to the subhalo distribution found by conventional subhalo finders that work in configuration space, and are in better agreement with recent gravitational lensing observations of the subhalo population in galaxy clusters. We have also used our results to investigate the distribution of haloes in different epoches and over different scales, to improve our understanding about the progenitor population of subhaloes. The merger tree built from HBT+ has also been used to study the dynamical status of Milky-Way size haloes.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
Our FY2017 studies have produced the software required for the project and have improved our understanding about the cold dark matter subhaloes. We have also developed a method to study the Lagrangian properties and formation histories of haloes. These progresses serve as the foundation and prototype of the warm dark matter subhalo analysis which will be conducted in the next fiscal year.
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| Strategy for Future Research Activity |
With the improved software and improved understanding about halo distribution and evolution in cold dark matter universe, the next step is to apply HBT+ to warm dark matter simulations and understand the evolution of warm dark matter subhaloes. We will start with the Aquarius-Warm simulation and explore how the linking-length parameter and halo tracking approach can be combined to remove spurious progenitor haloes. We will also compare the Lagrangian properties of real and spurious haloes to find diagnostics of spurious haloes. The HBT+ and FoF algorithms will be optimized to produce physical subhalo catalogues with high purity and completeness. The infall subhalo mass function and the tidal stripping models will be calibrated with these catalogues to produce the first physically-driven model of the warm dark matter subhalo distribution.
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| Causes of Carryover |
The incurring amount for the next Fiscal year will be used for attending workshop and conferences, academic visits and publications, as originally planned in the application form.
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Research Products
(4 results)
