Scientific Programs and Opportunities

Formation and Evolution of Galaxies

1Distant Galaxy 1 2Dwingeloo 3Distant Galaxy 2

"One of the most important programs in astrophysical cosmology is the determination of the sequence of events which has led to the large scale structure of the Universe as we know it today. The typical galaxies which will be observed in the deepest exposures with the Gemini telescopes emitted their light when the Universe was less than half its present age and, in many cases, at much earlier times. For many of the galaxies, multi-object spectrographs will enable their spectra and redshifts to be determined. The wide spectral coverage afforded by the Gemini telescopes from the ultraviolet through the optical to the infrared wavebands will enable detailed studies of the stellar populations of the faintest galaxies to be obtained. Furthermore, because of the high angular resolution of the telescopes in optical and infarared wavebands, the detailed internal structures of galaxies at these very great distances can be obesrved. These images will provide crucial evidence about the processes responsible fo the evolution of sprial and elliptical galaxies and why the galaxies seem to come in these distinct populations. The Gemini telescopes will enable the large scale structure of the distribution of galaxies to be determined at epochs significantly earlier than the present. According to some theories of the origin of the large-scale structure of the Universe, the distribution of galaxies should be significantly less clumpy in the distant past than it is now and we should be able to test this idea by studying the distribution of faint galaxies. Such studies should give a definitive answer to the question of whether the galaxies were formed by a process of hierarchal clustering of low mass objects, of whether they formed with roughly their present masses in the process of condensation from the intergalactic gas."

-Dr. Malcolm S. Longair, Chair of the Gemini Board 1994-1995

How did galaxies form and evolve in the Universe? Optical observations of the individual stars and star clusters in the Milky Way and nearby galaxies will provide the key to understanding the relation between stellar populations, chemical enrichment history, and the dynamical history of present day galaxies in the Universe. The Gemini telescopes will enable observations of extremely distant galaxies at IR wavelengths, covering the same rest wavelength range as optical observations of nearby galaxies. With the light gathering power and excellent image quality of the telescopes, it will be possible to make direct observations of the morphology, content, and composition of nascent and adolescent galaxies. Optical observations will reveal properties of the youngest stars in such systems. For cases where dust is present, much of the short wavelength energy emitted by young stars is absorbed and re-radiated in the thermal infrared.

This program is an example of one that requires broad band spectral coverage from the ultraviolet to the infrared. It requires excellent image quality and spectroscopic capability at optical and infrared wavelengths. It requires wide-field, multi-object capability for optical spectroscopy. Full sky coverage is also required. For example, the Magellanic Clouds, the nearest external galaxies, and the center of our own galaxy are in the southern hemisphere, while M31 and M33, the nearest spiral galaxies, are in the northern hemisphere.

Image Credits: 1:HST 2:INT 3:HST

Ruth A. Kneale / / February 27, 1998