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A.E. Reines, K.E. Johnson (University of Virginia)
Super Star Clusters (SSCs) and their constituent massive stars play an important role in the evolution of the universe through enriching the interstellar medium and triggering further star formation via supernova explosions. However, the birth of these objects is not well understood. We present our study of the ultra-young massive star clusters in the irregular starburst galaxy NGC 4449. Using observations spanning the optical to radio regimes, we probe the observable physical properties of these clusters as they emerge from their birth material.
Our VLA radio observations of NGC 4449 at centimeter wavelengths reveal dense HII regions associated with the massive natal star clusters in this galaxy. We compare these observations to infrared and optical images of NGC 4449 obtained from the HST archive. We use the clusters' spectral energy distributions in conjunction with stellar synthesis codes to estimate their ages, extinctions, and masses. The radio observations yield information about the total ionizing fluxes, the electron densities, and pressures in these natal environments. This study is part of a larger project that aims to unveil the earliest stages of SSC evolution by comparing and analyzing deeply embedded radio and infrared objects, and optically visible clusters in a large sample of extragalactic systems.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.