Star Formation: The Current Frontier

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Science  03 Mar 2000:
Vol. 287, Issue 5458, pp. 1557
DOI: 10.1126/science.287.5458.1557c

Star formation occurs by the collapse of a cloud of dust and gas. Spiral galaxies, which formed from collapsed clouds, have a dense nucleus or bulge dominated by older stars formed by an early, rapid burst of star formation. The spiral arms consist of gas, dust, and younger stars swirling outward away from the center. Many processes may trigger star formation, including gravitational interactions or shock waves from supernovae, but distinguishing between these processes is difficult without gaining more information about the composition and age distributions of stars in the galaxies.

Davidge has begun a survey in the near-infrared wavelength range of the Sc galaxies, the most “open” class of spiral galaxies, with the Canada-France-Hawaii Telescope (CFHT) adaptive optics bonnette (AOB) to determine the stellar structure of the centers of these galaxies and understand star formation processes. This initial study focuses on M33, the Triangulum galaxy, which is the third largest spiral galaxy in the Local Group (after the Milky Way and Andromeda). He has determined that there was a burst of star formation near the nucleus of M33 that occurred between 1 to 3 billion years ago. He also noted a recent episode of star formation in the nucleus, which is somewhat unexpected because M33 does not have a supermassive black hole at its center that might trigger star formation. Finally, he notes that the source of the gas for the recent star formation episode cannot be derived from the disk, which is chemically distinct from the young stars, so the collapsing gas is probably concentrated in the center. These results suggest that star formation is complex and variable, but more observations are needed to distinguish between the possible mechanisms that initiate the collapse.—LR

Astron. J.119, 748 (2000).

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