Star-UBB Seminar Series:- Cosmological QUOKKA - Quasar Observations on the Korean VLBI Network(KVN) from Korea to Australia
Measuring distances vs redshift (more commonly known as a Hubble Diagram) is one of the most fundamental yet difficult observations that can be made in astronomy. Every time the diagram has been extended to greater and greater distances (or higher redshifts), important discoveries have been made. Most recently this was the accelerating expansion of the universe, for which the 2011 Nobel Prize was awarded. he is asking the simple question: "what happens if we look further?".
The discovery of the accelerated expansion of the universe was accomplished using Type Ia supernovae, but they are based on the 'distance ladder' and can only be seen to a redshift of ~2. Active Galactic Nuclei(AGN) are unique objects as they can be seen at both low redshift (z~0) and high redshift (z~6). For this reason, they have long been sought as a distance measure with limited success. It is within this context that the speaker and his team are beginning the Cosmological QUOKKA project. The core assumption is that the radio variability observed is constrained by the speed of light. Multiplying the timescale of variability by the speed of light gives a linear size estimate which can then be compared against the apparent size using Very Long Baseline Interferometry(VLBI). In this presentation, the speaker will describe the method, some early results (including a measurement of the Hubble Constant) and the details of our observational project using the Korean VLBI Network and the Mopra telescope in Australia and potentially South Africa.
講者：Jeffrey Adam Hodgson (韓國 世宗大學 Sejong University, Department Astronomy)
Scientific and Technological Advanced Research- Babeș-Bolyai University(Star-UBB) Seminar Series in Gravitation, Cosmology and Astrophysics
Presently a period of rapid and intense change are being witnessed in our understanding of the gravitational force, at a rate that is quickly increasing since the important observational discoveries of the late 1990s. With the advent of new observational techniques, the emergence of important cosmological and astrophysical paradigms can be seen that lead to a deep change in our understanding of the Universe. Astronomical observations strongly suggest that at large scales the force of gravity may not behave according to standard general relativity, and that a generalization of the gravitational action, either at the geometric level, or at the matter level, may be required for a full understanding of the gravitational interaction.
The goal of the present seminar is to bring Theoretical Gravitational Physics closer to the observations and experiments, and to discuss current topics in general relativity, high-energy physics, astrophysics and cosmology.