Galaxies and their Masks (PDF)

Various kinds of masks obscure our view of our galaxy, the Milky Way, as well as of other galaxies. Masks of interstellar dust affect our measurements within galaxies, on scales ranging from individual supernovae to the galaxies themselves. The "mass mask" (our inability to image mass rather than light) gives astronomers a very incomplete picture of the size and structure of galaxies themselves, because we cannot image the dark matter which provides most of the galactic mass. Another mass is the "dynamical mask": as galaxies form, much dynamical information is lost in the birthing process. A new thrust in research is to retrieve such information by means of chemical tagging. About 50 astronomers flew into Namibia in April 2010, to celebrate the 70th birthday of Professor K.C. Freeman, Fellow of the Royal Society. At age 70, Freeman, a father of dark matter in galaxies, continues to be one of planet's most highly cited astronomers. The current volume affords readers a unique perspective on galaxies by probing the thoughts of some of the greatest astronomers of our age. Contributions focus on galaxies from within our Local Group to those in our high redshift Universe. Approximately 40 in-depth review and contributed papers are contained in the volume, each written by an expert in the field. Two unusual features of the current volume include the "Star Country" of the San people of southern Africa as well as the introduction into astronomy of "The Treachery of Images" by the Belgian surrealist artist René Magritte. "Everything we see hides another thing, we always want to see what is hidden by what we see", said Magritte. These words resonate the theme of the current volume "Galaxies and their Masks", which is written at a level to be appreciated by both specialist and doctoral student alike.