And since the color and brightness of young clusters gives their ages--and therefore, the time since a collision began--astronomers hope to put together a series of snapshots of the entire collision process by looking at many examples of merging galaxies.
Nearby examples of (dwarf) irregular galaxies include the Magellanic Clouds.
In this talk, I give an overview of very early results on galaxies, including examples of normal spirals, actively star-forming and interacting galaxies, and E and S0 galaxies.
Mining the resulting terabyte or so of data will allow astronomers to investigate the evolution of galaxies, for example, since the SDSS will provide an enormous sample of them.And even the SDSS will represent only a single snapshot of the sky.
Laherrère and Sornette (1998) describe the general property of concentration in nature, and give as examples the radio and light intensity of galaxies (a small proportion of galaxies emit a large proportion of the radio and light observed) and oil field size in the Gulf of Mexico (most fields are small, but a relatively few fields have much of the oil).
Furthermore, the populations vary with galaxy mass; while the Milky Way Galaxy, a massive example of a spiral galaxy, contains no stars of young age and a low heavy-metal abundance, low-mass galaxies, such as the dwarf irregulars, contain young, low heavy-element stars, as the buildup of heavy elements in stars has not proceeded far in such small galaxies.
Their hope is to see examples of the earliest stars and galaxies and study their evolution and the production of elements, which in turn leads to better understanding of the origins of life.
For example, from space astronomers could 'hear' the formation of galaxies in the early days of the Universe.
For example, in this photo from the Hubble Space Telescope, a cluster of galaxies acts as a gravitational lens, magnifying a single galaxy far, far beyond it, which would ordinarily be invisible to us.
The Great Wall, a vast supercluster of galaxies over 500 million light-years wide, provides a dramatic example of a large-scale structure that redshift surveys can detect.
