Title：Ionisation front dynamics and propagation in galactic enviroments in the young Universe
Speaker：Kinwah Wu (University College London, UK；Visiting Professor)
Abstract：Our Universe was filled with neutral hydrogen and helium after a recomination 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 first stars and by the X-rays production in the accretion of matter into compact objects. These compact objects include the stellar mass black holes, which were remnants of the massive stars, and the supermassive black holes which resided at the centre of galaxies. When the Universe became transparent to optical light again, its allowed starlight to travel through large distances to reach us. The re-ionisation era is one of the least understood periods in the cosmological history. It is where galaxies, like our Milky Way, were in an infant stage, rapidly turning the gases trapped within it into stars.
In this talk I will discuss the ionisation proecesses in the protogalaxies and their host enviroments. Although it is commonly believed re-ionisation was mainly driven by the irradiation of UV/X-rays of the cosmological neutral media from the massive stars and the accreting compact objects, the bombardment of ultra-high-energy particles generated in the violent processes associated with star formation and accretion could also play a non-negligible role in determining the evolutionary history of galaxies. I will show how ionisation fronts in sub-galaxy and larger scales form, develop and propagate in the presence of radiative heating and high-energy particle bombardments. I will also discuss the corresponding astrophysical implications.
Time：24 June (Friday), 10:00am
Place：Room 212, Astronomy Building
欢迎各位老师、同学参加！
南京大学天文与空间科学学院
