本文章最後由 iheby 於 2016-11-20 09:14 編輯
潮汐崩潰事件作為超愛丁頓極限光度黑洞吸積的探測器 @香港中文大學物理系
SEMINAR:- Tidal Disruption Events as a Probe of Super-Eddington Accretion onto Black Holes
The tidal disruption of a star by a massive black hole provides a unique opportunity for us to understand the physics of accretion onto black holes. So far about 50 tidal disruption events (TDEs) have been detected using X-ray, UV, optical and radio telescopes. In the first few months of the burst, the rate that stellar materials is supplied to the black hole can greatly exceed the Eddington accretion rate, giving us a perfect window to peek into super-Eddington accretion. The understanding of super-Eddington accretion, such as whether the Eddington luminosity limit can be violated, has important implications for black hole growth and galaxy evolution in the early universe. In this talk, the speaker will first give a brief summary of the observational status of TDEs. Then she will give an introduction to the TDE physics, and present their theoretical calculations on what parameters of the black hole and star can make super-Eddington accretion happen. Lastly, the speaker will talk about their ongoing general relativistic radiation magnetohydrodynamics simulations of superEddington accretion disks in the context of TDEs. Results from these simulations can explain some previously poorly understood observational properties of TDEs, and can be applied to study other astrophysical systems such as active galactic nuclei and X-ray binaries.
時間：2016.11.22(二) 15:30 ~ 16:15
地點：香港中文大學 科學館北座G25室
講者：戴麗心 博士 Dr. Lixin Jane DAI (Department of Physics University of Maryland, USA)
語言：英語
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以中紅外波段選取觀測的活躍星系核 @香港中文大學物理系
SEMINAR:- Infrared selected AGNs
The speaker will present our recent results on mid-infrared selected active galactic nuclei (AGNs). They derived their stellar masses, star formation rates, dust properties, AGN contribution, as well as obscuration by fitting their optical to far-infrared photometry through the state-of-art spectral energy distribution (SED) technique. They explored the morphologies of their hosts through HST images and found that AGN hosts are more compact, especially for our obscured type-2 IR AGN sample, comparing to normal star-forming galaxies at similar redshift and stellar mass. They postulate that obscured AGNs are hosted by galaxies experiencing a mode of compaction, as recently discussed in the literature from hydrodynamic simulations of gas-rich disk galaxy formation.
時間：2016.11.16(三) 15:30 ~ 16:30
地點：香港中文大學 科學館北座311室
講者：張雨晏 博士 Dr. Yu-Yen CHANG (台灣中央研究院天文及天文物理研究所)
語言：英語
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年輕宇宙銀河環境中的流、加熱與及電離前緣傳播 @香港中文大學物理系
SEMINAR:- Outflow, Heating and Ionisation Front Propagation in Galactic Environments in the Young Universe
Our Universe was filled with neutral hydrogen and helium after a recombination era that followed the big bang. In this epoch, the Universe was cold, dark and opaque to optical light. However, it underwent a phase transition, when the first stars began to shine and the first quasars emerge. The neutral gas was re-ionised by the strong UV radiation emitted from the stars and by the X-rays production in the accretion of matter into compact objects. When the Universe became transparent to optical light again, it allowed starlight to travel over a large distance to reach us. The reionisation era is one of the least understood periods in the cosmic history. It is when galaxies, like our Milky Way, were in an infant stage, rapidly turning the gases into stars. In this talk, the speaker will discuss the dynamical of outflow from galaxies, the ionisation processes in galactic environments and how ultra-high-energy particles generated in the violent processes associated with star formation and accretion would affect the early evolution of galaxies. The speaker will also show how ionisation fronts in sub-galaxy and larger scales form, develop and propagate in the presence of radiative heating and discuss the corresponding astrophysical implications.
時間：2016.11.16(三) 16:30 ~ 17:15
地點：香港中文大學 科學館L5演講廳
講者：胡建華 教授 Prof. Kinwah Wu (Mullard Space Science Laboratory University College London, UK)
語言：英語
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