Title: Adaptive Optics in the 21st Century
Location：303(third floor of Astronomy Building)
Time: 10 AM, Oct 24 (Monday)
Speaker: Edward Kibblewhite
In this talk I will summarize progress made in adaptive optics for astronomy up to today and describe how I see its development in the future. I will discuss in some detail the challenges of laser beacon adaptive optics and the general complexity of the technology. I will discuss possible viable options for the 12 m China telescope.
Title: Recent Progress in Weak Lensing Measurement
Location: The Lecture Hall(third floor of Astronomy Building)
Date & Time: 3 PM, Oct 27 (Thursday)
Speaker: Prof. Jun Zhang (张骏)，Shanghai Jiao Tong University
Weak lensing is an important probe of the cosmic structure and the scale evolution of our Universe. We show that the weak lensing effect (also called cosmic shear) can be measured accurately from background galaxy images through Fourier transformation in the presence of background noise, source Poisson noise, and finite pixel size, without assumptions on the morphologies of galaxy and PSF. More recently, we have further optimized the way of taking the ensemble average of the cosmic shear signal, and the way of measuring the point-spread-function at the positions of the galaxies. We show some preliminary measurement results using the CFHTlens data, and demonstrate that our method is the most promising technique for cosmic shear measurement in the ongoing and upcoming large scale galaxy surveys.
Title: "Fast vs. Slow: Galaxy Death at z ~ 2 vs. z ~ 0"
Location: The Lecture Hall (third floor of Astronomy Building)
Date & Time: 10 AM, Oct 28 (Friday)
Speaker: Prof. Sandra Faber (UC Santa Cruz)
Evidence indicates that galaxies live through a life cycle in which they start out gas-rich, consume their gas in star formation, and then stop making stars (quench). Why star formation falls so low is not clear. It is true that there is less gas falling onto galaxies at late times, but not much gas is needed to keep them blue, yet observed star-formation rates after quenching are very low. Recent observations at z ~ 2 and z ~ 0 have identified sequences of galaxies that appear to be in the process of quenching, and studying these sequences has shed light on the physics of quenching. Galaxies at z ~ 2 appear to fade on a "fast track" after experiencing feedback from central starbursts and black hole growth triggered by sudden "compaction" events. Galaxies at z ~ 0 (today) in contrast appear to quench on a "slow track" owing to gradually increasing feedback from a much more slowly growing central BH. Remarkably, quenching in both cases appears to be associated with reaching nearly the same central threshold stellar density. Early gas-rich galaxies cross this
threshold rapidly due to copious gaseous dissipation, whereas late, gas-poor galaxies must depend on slowly acting secular evolution processes, such as bars and spiral arms, that gradually bring gas to the center to make stars and (presumably) build the black hole. On both tracks, it appears that central stellar buildup and black hole growth proceed together in nearly the same way despite the large difference in speed and physical processes.