When worlds collide: Cornell astronomers investigate cosmic forces that produce new galaxies

http://www.news.cornell.edu/stories/Nov05/Higdon.Spitzer.lg.html

Nov. 30, 2005

By Lauren Gold
lg34@cornell.edu

When galaxies collide (as our galaxy, the Milky Way, eventually will with the nearby Andromeda galaxy), what happens to matter that gets spun off in the collision's wake?

With help from the Spitzer Space Telescope's infrared spectrograph (IRS), Cornell astronomers are beginning to piece together an answer to that question. Specifically, they are gaining new insight into how some ubiquitous dwarf galaxies form, interact and arrange themselves into new systems.

Dwarf galaxies, with stellar masses around 0.1 percent that of the Milky Way, are far more common than their more massive spiral or starburst counterparts. Some may be primordial remnants of the big bang; but others -- called tidal dwarfs -- formed later as a result of gravitational interactions after galactic collisions.

To understand which dwarf galaxies are tidal in origin and how those galaxies differ from primordial dwarf galaxies, Cornell researcher Sarah Higdon and her colleagues studied a system called NGC 5291, which is 200 million light years from Earth and stretches a distance roughly four times the span of the Milky Way. At the system's center are two colliding galaxies; behind them trail a string of much smaller dwarfs.