|Preface and Acknowledgements:|
In the early 1930s Karl Jansky1 detected the center of our Galaxy in radio waves at a wavelength of 14.6 m or a frequency of 20.5 MHz.
Until this time all observations of galaxies had been made in the optical region, which has radiation with wavelengths between 330 and 800 nanometers. Galaxies that can be seen by eye, appearing as faint, cloud-like objects, are the two Magellanic Clouds (named after the Portuguese explorer Ferdinand Magellan) in the Southern Hemisphere and the Andromeda galaxy (NGC224 or Messier 31) in the Northern Hemisphere. Observers with very good eyesight may also detect NGC598/M 33, in the constellation Triangulum. We also get a myopic view of nearby stars (about six thousand within a few thousand light-years) and a wide-field view of diffuse light, 'the Milky Way', from distant stars, near the plane of our own Galaxy.
Since the early 17th century, telescopes have provided higher resolution observations to fainter brightness levels than possible with the eye. In 2009 the world celebrated the International Year of Astronomy (IYA), as sanctioned by the United Nations and directed by the International Astronomical Union partly to celebrate four hundred years of telescopic observations since the initial endeavors of Thomas Harriot and Galileo Galilei.
In terms of effective galaxy research tools, we had to wait until the mid-19th century for large telescopes to be built. Observations by eye, photography and by spectroscopy all played vital roles. The Andromeda galaxy and others, became known as 'spiral nebulae' and came under close scrutiny. The nature and content of the spiral nebulae were increasingly debated until the mid-1920s when their true distances were revealed. The spiral nebulae were not part of our Galaxy, which many had thought constituted the universe. They were separate, distant galaxies in their own right. Almost overnight, the true nature of the universe was discovered. Our Galaxy was one of billions.
Since Janskys breakthrough in the early 1930s astronomers interested in studying the formation and evolution of galaxies have rapidly ventured into other regions of the electromagnetic spectrum. In 1951 Ewen and Purcell discovered 21 cm radio emission from interstellar hydrogen, as predicted by Van de Hulst in 1945. In 1961 the satellite Explorer 11, detected 22 events from high energy Gamma rays (and 22,000 events due to charged cosmic rays!). The first extrasolar X-ray source was detected in 1962 using a sounding rocket by the X-ray astronomy group at American Science and Engineering. In the late 1960s Neugebauer and Leighton completed the first major near-infrared survey of the sky. From 1968 onwards Orbiting Astronomical Observatory (OAO) satellites provided the first detections of sources in the ultraviolet. In 1987 the James Clerk Maxwell Telescope (JCMT) began dedicated observations in the submillimeter region. The optical and near-infrared regions have also benefited by advances in instrumentation and active and adaptive optics on the latest generation of very large ground-based telescopes. Near diffraction limited observing has been achieved by placing telescopes above the Earths atmosphere (e.g. Hubble Space Telescope since 1990).
Radiation from all regions of the electromagnetic spectrum has now been detected from galaxies. These observations have utilized telescopes at ground-based observatories (many located at high altitude mountain sites), telescopes in aircraft (> 10 km altitude), detectors on balloons that voyaged to the upper atmosphere (30-40 km altitude), instrument payloads on rockets that reached space, observatory satellites in Earth and Solar orbit as well as instruments aboard planetary missions journeying through the Solar System.
This atlas is a compendium of galaxy images spanning the Gamma ray, X-ray, Ultraviolet, Optical, Infrared, Submillimeter and Radio regions of the electromagnetic spectrum. Explanatory text describes how different radiation is produced, which objects (i.e. cold, warm or hot gas, dust, stars, particles, atoms and molecules) it originates from, and what types of telescopes are used to detect it. The galaxies are divided into categories of Normal, Interacting, Merging, Starburst and Active, though many have been classified across one or more categories.
The purpose of this atlas is to display and describe some of the best multiwavelength images of galaxies. The images originate from a variety of telescopes, instruments and detectors, and therefore possess wide ranges of signal-to-noise2, angular resolution, sampling or pixel sizes and fields of view.
The atlas consists of four parts. The first part introduces galaxies, discusses the atlas sample, categories of galaxies and properties of the sample. Part two describes the various origins of radiation emitted by galaxies and presents some important galaxy research topics that use multiwavelength observations. Part three discusses multiwavelength radiation from the Galactic Center and finishes with all-sky multiwavelength images of our Galaxy. Part four comprises the multiwavelength atlas images with scientific descriptions from the literature. The book concludes with appendices describing telescopes and instruments, image sources, technical descriptions of each image, a cross-reference list of galaxies, and example plots of spectral energy distributions. General text references and atlas galaxy references are also given.
The images presented will help the general reader appreciate the incredible information content of multiwavelength observations without needing an extensive scientific or mathematical background. The accompanying text provides specific discussion of galaxy properties, and astronomical radiation origins and processes useful for those wanting more astrophysics content. Research summaries of individual atlas galaxies are given for those interested in more detailed multiwavelength information.
I would appreciate correspondence from researchers who may have relevant information and/or images.
Glen Mackie, gmackie at swin.edu.au, Centre for Astrophysics and Supercomputing, Swinburne University of Technology, December, 2009, IYA
1Jansky, K.G. 1933, 'Electrical Disturbances Apparently of Extraterrestrial Origin', Proceedings of the IRE 21, 1387., Jansky, K.G. 1933, 'Radio waves from outside the solar system', Nature, 132, 66.
2Signal-to-noise is a measure of the amount of detected radiation from a source above the inherent radiation or noise of the detector and background signal.
This atlas has come about due to the generosity of many astronomers that have kindly provided their data and information about their observations. I would like to thank
P. Amram, P. Barthel, R. Beck, L. Blitz, M. Birkinshaw, G. Bothun, G. Bower, A. Bridle, U. Briel, E. Brinks, M. Burton, H. Bushouse, B. Canzian, C. Carilli, J. Chapman, P. Choi, J. Condon, P. Cox, P. Crane, T. Dame, R. Diehl, S. Digel, S. Dobereiner, M. Dopita, N. Duric, E. Dwek, M. Ehle, G. Fabbiano, E. Feigelson, L. Ferrarese, D. Finkbeiner, K. Freeman, P. Guhathakurta, R. Genzel, M. Haas, D. Hartmann, R. Haynes, D. Heeschen, J. P. Henry, J. Hibbard, H. Hippelein, S. Holmes, J. C. Howk, J. Holtzman, Hubble Heritage Team, A. Hughes, E. Hummel, J. Hutchings, G. Jacoby, S. Jorsater, N. Junkes, P. Kahabka, J. Kamphuis, W. Keel, D. Kelly, N. Killeen, U. Klein, B. Koribalski, K. Kraemer, M. Kramer, M. Krause, R. Laing, S. Larsen, D. Leisawitz, G. Lewis, L. Lindegren, Local Group Survey Team, B. Madore, P. Massey, A. Mattingly, D. Maoz, A. Marlowe, A. McConnachie, S. McGaugh, K. McLeod, MCELS Team, D. Meier, K. M. Merrill, G. Meurer, C. Mundell, N. Neininger, R. Norris, U. Oberlack, K. Olsen, A. Pedlar, R. Perley, W. Pietsch, J. Pinkney, P. Planesas, R. Pogge, S. Points, M. Putman, R. Rand, S. Raychaudhury, T. Rector, M. Regan, W. Rice, G. Rieke, M. Rieke, A. Rots, M. Rubio, S. Ryder, B. Savage, E. Seaquist, E. Schlegel, S. Schoofs, N. Scoville, E. Shaya, S. Shostak, C. Smith, S. Snowden, W. Sparks, S. A. Stanford, L. Staveley-Smith, R. Supper, R. Sutherland, P. Thaddeus, R. Tilanus, S. Tingay, G. Trinchieri, J. Trumper, B. Tully, J. Turner, J. Ulvestad, E. Valentijn, J. van der Hulst, G. van Moorsel, L. Vigroux, A. Vogler, W. Walsh, R. Walterbos, B. Whitmore, R. Wielebinski, A. Wilson, F. Winkler, T. Wong, J. Wrobel, C. M. Young, and H. Zimmermann.
Credits for atlas image observers and data owners are also summarized in Appendix C.
Seth Digel (GSFC) was of great assistance in providing many of the Astrophysics Data Facility all-sky images of the Galaxy and reformatting several images. Karen Smale (LHEA), Kathy Lestition (Chandra X-ray Observatory Center), Dan Brocious (Smithsonian Institution, Whipple Observatory), Catherine Ishida (Subaru Telescope) and support staff at STScI helped with my many enquiries. I worked on the beginnings of this atlas whilst visiting the Anglo-Australian Observatory and I thank the then Director, Prof. Brian Boyle for his hospitality.
I would also like to thank the editorial staff at Cambridge University Press, especially Adam Black for his initial interest in the atlas and Vincent Higgs and Lindsay Barnes for their expert guidance to get it to completion.
The construction (construction tends to more adequately describe the process of producing this atlas than writing!) and presentation of this work were greatly improved due to the keen eye of my wife, Corinne. She quizzed me on many statements during enthusiastic readings of the chapters. I thank her for wonderful support and encouragement.
I hope this atlas represents a tribute to the rapid progress made in multiwavelength observations of galaxies and credit is due to all astronomers involved in this type of research. It was always heartening to hear support from astronomers who corresponded with me about the atlas during its construction, and who were extremely generous with their time and knowledge: many thanks to Rainer Beck, John Hibbard, Annie Hughes, Phil Massey and Sean Points.
I received valuable comments on drafts of this atlas from astronomers Chris Flynn, Virginia Kilborn, Bill Keel, Malcolm Longair, Emma Ryan-Weber and Steve Tingay which greatly improved the final product. I have also benefited from comments from anonymous referees appointed by Cambridge University Press. Any errors or omissions remaining, are entirely my responsibility. G.M.