Monday 15 Apr 2019: [Seminar] The resonant structure of galaxy discs
Prof. John Beckman - IAC (Instituto de Astrofísica de Canarias)
4th Floor, Physics Building 14:00-15:00
We have developed in my research group a method for measuring the corotation radius within a galaxy disc. It is based on the change in the geometry of orbits from prolate to oblate elipses as corotation is crossed, which gives rise to a measurable phase change in the radial flow of gas (and in fact stars) from inwards to outwards, or vice versa. Using two-dimensional high resolution emission spectra across the full face of a galaxy obtained with Fabry-Perot spectroscopy, we can carry out the necessary analysis and make an accurate determination of corotation. In a sample of some 150 galaxies analyzed in this way we find more than one corotation per galaxy, even in unbarred galaxies. In the talk I will describe the method, compare its results with the "classical" Tremaine Weinberg method for pattern speed determination, and go on to show applications to the evolutionary history of bars, and to relations between pitch angle, bar strength and resonances, which favour the swing amplification models for disc-bar evolution.