Morphological And Physical Classification Of Galaxies

The morphological scheme devised by Hubble and followers to classify galaxies has proven over many decades to be quite effective in directing our quest for the fundamental pa rameters describing the extragalactic manifold. This statement is however far more true for spirals than for ellipticals. Echoing the concluding remarks in Scott Tremaine's sum mary talk at the Princeton meeting on Structure and Dynamics of Elliptical Galaxies, "the Hubble classification of spirals is useful because many properties of spirals (gas con tent, spiral arm morphology, bulge prominence, etc. ) all correlate with Hubble time. By contrast, almost nothing correlates with the elliptical Hubble sequence El to E7. " During the last few years much effort has been put into the search for a more meaningful classification of ellipticals than Hubble's. Concomitantly, forwarded by some provocative conjectures by R. Michard, the classical question of whether E galaxies form a physically homogeneous family has been brushed up once more. Results of these and other parallel studies look rather promising and point to suture part of the dichotomy between ellipticals and disk galaxies which had become popular in the early eighties, owing to dynamical arguments. At the same time it appears more and more clear that, besides the usual genetic varieties of galaxies, products of environmental evolution must also be contemplated in building our modern picture of the "reign of galaxies" . The above considerations prompted us to solicit Prof.

A concise and up-to-date guide to the shape of galaxies and how they can be classified, by one of the pioneers of the field.

New illustrated atlas on modern galaxy classification for astronomy researchers, students, and amateurs.

In order to outline possible future directions in galaxy research, this book wants to be a short stopover, a moment of self-reflection of the past century of achievements in this area. Since the pioneering years of galaxy research in the early 20th century, the research on galaxies has seen a relentless advance directly connected to the parallel exponential growth of new technologies. Through a series of interviews with distinguished astronomers the editors provide a snapshot of the achievements obtained in understanding galaxies. While many initial questions about their nature have been addressed, many are still open and require new efforts to achieve a solution. The discussions may reveal paradigms worthwhile revisiting. With the help of some of those scientists who have contributed to it, the editors sketch the history of this scientific journey and ask them for inspirations for future directions of galaxy research.

South Africa - a land of paradigm shifts. A land where we are willing to leave behind the old, to bravely accept the new. What do we need to exit the dark ages in the morphology of galaxies? How prevalent is the cherishing of old concepts? Traditional morphology has been `mask-oriented', focusing on masks of dust and gas which may constitute only 5 percent of the dynamical mass of a galaxy. Some of the world's foremost astronomers flew to South Africa to address morphologically related issues at an International Conference, the proceedings of which are contained in this volume. Examine predicted extinction curves for primordial dust at high redshift. Stars evolve; why not dust? Read about the breakdown of the Hubble sequence at a redshift of one. Explore the morphology of rings; the mysteries of metal-rich globular clusters; vigorous star-formation in the Large Magellanic Cloud; the world of secular evolution, where galaxies change their shapes within one Hubble time. And much more. Examine a new kinematical classification scheme of the unmasked, dust-penetrated near-infrared images of spiral galaxies. This volume contains over 80 refereed contributions (including 18 in-depth keynote review articles), 40 pages of questions and answers, a panel discussion transcribed from tape and 24 colour plates. The volume is unique in that contributions from both high and low redshift experts are represented at a level readily accessible to postdoctoral students entering the exciting world of morphology - whether it be of the local, or more distant, Universe.

No modern astronomer made a more profound contribution to our understanding of the cosmos than did Edwin Hubble, who first conclusively demonstrated that the universe is expanding. Basing his theory on the observation of the change in distanct galaxies, called red shift, Hubble showed that this is a Doppler effect, or alteration in the wavelength of light, resulting from the rapid motion of celestial objects away from Earth. In 1935, Hubble described his principal observations and conclusions in the Silliman lectures at Yale University. These lectures were published the following year as "The Realm of the Nebulae," which quickly became a classic work.