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分子雲衝突と銀河の星形成に関する数値的研究
Get PDFGalaxies are fundamental constituents of the Universe, evolving through the process of star formation by consuming gas inside giant molecular clouds (GMCs). Recent observations and numerical simulations have suggested that cloud-cloud collisions (CCCs) play a crucial role in compressing gas at collision fronts, leading to the efficient formation of massive stars. In this study, we perform numerical hydrodynamical simulations of isolated disk galaxies with sufficiently high resolution to resolve individual GMCs. We investigate the impact of star formation triggered by CCCs on the global star formation in isolated disk galaxies and the GMC properties. Our study is summarised as follows. Cloud-cloud collisions triggering star formation in galaxy simulations (Chapter 3) Aim. Previous studies on CCCs in galaxy simulations relied on post-processing analysis, lacking the ability to self-consistently consider the promoted star formation and the subsequent stellar feedback. In our approach, we address this limitation by detecting CCC events on-the-fly in galaxy simulations with the prescription of star formation and stellar feedback. Through this novel methodology, we explore the effect of star formation triggered by CCCs on galaxy evolution and GMC properties. Methods. We develop an on-the-fly CCC identification algorithm for the simulation code Gizmo, which encompasses the solver for gravity and Lagrangian hydrodynamics. In addition, we make a model of star formation triggered by CCCs based on insights obtained from previous simulations of CCCs. Using the CCC identification algorithm, we perform two simulations of an isolated disk galaxy – one with and one without the star formation model. Our investigation focuses on the impact of CCC-triggered star formation on star formation rates (SFRs), the Kennicutt-Schmidt (KS) relation, and GMC properties. Furthermore, we explore the differences in CCC properties between postprocessing and our on-the-fly identification of CCC events. Characteristics. This work marks the pioneering effort to establish a connection between CCCs and induced star formation within galaxy simulations. The implementation of our on-the-fly CCC identification algorithm enables us to investigate the importance of CCCs in the context of galaxy simulations. Results. In the simulation with the CCC-triggered star formation model, ∼ 70% of stars are born in colliding GMCs, while in the simulation without the model, the fraction is ∼ 50%. The KS relation exhibits a steeper slope in the simulation with the model due to the promoted star formation in colliding GMCs. When CCCs are identified using the on-the-fly algorithm, CCC properties such as collision speeds and frequencies are not significantly impacted by the star formation model. However, the collision frequencies computed through the post-processing analysis can be underestimated by a factor of ∼ 8 compared to the on-the-fly analysis. Given these findings, we recommend investigating CCC-driven star formation and galaxy evolution in simulations using the on-the-fly CCC identification algorithm
トウモロコシタンパク質由来 GLP-1 分泌誘導成分の同定および有効性に関する研究 [全文の要約]
Get PDFこの博士論文全文の閲覧方法については、以下のサイトをご参照ください。https://www.lib.hokudai.ac.jp/dissertations/copy-guides
グアニン四重鎖構造形成CpGオリゴデオキシヌクレオチドの免疫活性化機能に対する複合体の構成とサイズの影響に関する研究 [全文の要約]
Get PDFこの博士論文全文の閲覧方法については、以下のサイトをご参照ください。【担当：理学部図書室】https://www.lib.hokudai.ac.jp/dissertations/copy-guides