Denuded Dwarfs

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Science  27 Aug 2004:
Vol. 305, Issue 5688, pp. 1215
DOI: 10.1126/science.305.5688.1215a

Globular clusters of stars are ubiquitous and provide important clues about galaxy formation. They also are large and luminous, and hence one of the easier kinds of sub-galactic objects to study. They all “look” the same; that is, they have scale radii, surface brightness, and velocity dispersion properties that are similar from one globular cluster to the next, suggesting that they all formed in the same fashion. But how do millions of stars come together into a relatively featureless glob?

Martini and Ho observed 14 new globular clusters in a large elliptical galaxy, Centaurus A, and estimate that these clusters are almost as massive as dwarf galaxies. In fact, the clusters have properties so similar to those of the centers of dwarf galaxies that the authors conclude the clusters might actually be the naked cores of dwarf galaxies. In other words, these shapeless clusters might once have been beautifully structured galaxies that were tidally stripped of their finery. Such a reclassification would alter hierarchical models of galaxy formation and enhance the importance of near- collisions between galaxies that lead to tidal stripping. — LR

Astrophys. J. 610, 233 (2004).

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