Where star formation takes placeIn some cases, starburst galaxies have star-forming rates of hundreds of solar masses per year, corresponding to an exhaustion timescale of the order of 100 million years (about 1% the age of the universe). It follows that observed starbursts must have started in the relatively recent past. The burst may be galaxy-wide or confined to a small region, less than 1,000 light-years across, about the nucleus. Typically, much of the star formation occurs in very luminous, compact star clusters, 10 to 20 light-years across, with luminosities up to 100 million times that of the Sun. These clusters, known as ultra-luminous clusters are the most dense and intense star-forming environments known, and may be analogues of typical objects in the early epochs of galaxy formation. If they remain gravitationally bound after the mass loss from massive members is complete, they may eventually come to look a great deal like globular clusters.
SuperwindsThe rapid rate of supernova explosions in starburst galaxies produces expanding bubbles of multimillion degree gas. When the starburst is sufficiently intense, it can create a superbubble so hot and energetic that it expands out of the galaxy in what is called a superwind.
Superwinds are thought to contain the carbon, nitrogen, oxygen, iron and other heavy elements dispersed by supernovas and spread these elements throughout the space between galaxies.
Signatures of starburst galaxiesObservationally, the overwhelming signature of starburst galaxies is intense emission in the far-infrared, caused by the ultraviolet emitted by numerous hot, young stars being absorbed by dust and reemitted at longer wavelengths. At these wavelengths, and to a lesser degree in the radio region, starburst galaxies rank second only to active galactic nuclei (AGN). The two types can readily be told apart, however: a compact, flat-spectrum radio source indicates an AGN, while more diffuse radio emission suggests a star-forming nucleus. Furthermore, AGN are more radio-loud and show high-ionization species, whereas the lack of these species combined with the presence of diffuse interstellar bands, due to molecules that are destroyed by the intense hard radiation in AGN, point to a starburst.
Related category GALAXIES
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