Toward an internally consistent astronomical distance scale

Accurate astronomical distance determination is crucial for all fields in astrophysics, from Galactic to cosmological scales. Despite, or perhaps because of, significant efforts to determine accurate distances, using a wide range of methods, tracers, and techniques, an internally consistent astronomical distance framework has not yet been established. We review current efforts to homogenize the Local Group's distance framework, with particular emphasis on the potential of RR Lyrae stars as distance indicators, and attempt to extend this in an internally consistent manner to cosmological distances. Calibration based on Type Ia supernovae and distance determinations based on gravitational lensing represent particularly promising approaches. We provide a positive outlook to improvements to the status quo expected from future surveys, missions, and facilities. Astronomical distance determination has clearly reached maturity and near-consistency.Comment: Review article, 59 pages (4 figures); Space Science Reviews, in press (chapter 8 of a special collection resulting from the May 2016 ISSI-BJ workshop on Astronomical Distance Determination in the Space Age

Experimental determination of the excitation energy of superdeformed bands in 192,194^{192,194}Hg by analysis of the decay quasicontinuum γ\gamma rays

Superdeformed bands in the mass A = 190 region decay suddenly, over a few states, at relatively low spin and high excitation energy. The decay path is very fragmented and only in a few cases have one-step or two-step decays been seen. Thus, only three superdeformed bands have so far been linked to the normal states they decay to. Most of the γ rays from the decay form an unresolved quasicontinuum spectrum. This paper describes the extraction of the total quasicontinuum decay spectrum that connects the superdeformed and normal yrast states. It also demonstrates that the excitation energy and spins of superdeformed bands can be determined by analyzing this total decay spectrum. The analysis method is first tested in 194Hg, which is one of the few cases where the excitation energy and spin of the yrast superdeformed band are known, and is then applied to the yrast superdeformed band in 192Hg, where no one-step decays have been seen thus far