Variation of the IMF

Abstract

(abridged) The {stellar IMF} has been found to be essentially invariant. While some apparent differences are seen, the uncertainties inherent to this game do not allow a firm conclusion to be made that the IMF varies systematically with conditions. The IMF integrated over entire galaxies, however, is another matter. Chemical and photometric properties of various galaxies do hint at {galaxial IMFs} being steeper than the stellar IMF, as is also deduced from direct star-count analysis in the MW. These results are sensitive to the modelling of stellar populations and to corrections for stellar evolution, and are thus also uncertain. However, by realising that galaxies are made from dissolving star clusters, star clusters being viewed as {the fundamental building blocks of galaxies}, the result is found that galaxial IMFs must be significantly steeper than the stellar IMF, because the former results from a folding of the latter with the star-cluster mass function. Furthermore, this notion leads to the important insight that galaxial IMFs must vary with galaxy mass, and that the galaxial IMF is a strongly varying function of the star-formation history for galaxies that have assembled only a small mass in stars. Cosmological implications of this are discussed.

13 pages, to appear in IMFat50: The Initial Mass Function 50 years later, ed: E. Corbelli, F. Palla, and H. Zinnecker, Kluwer Academic Publishers; a meeting held at the Abbazia di Spineto, Tuscany, Italy -- May 16-20, 2004

References in corpus (10)

• Embedded Clusters in Molecular Clouds
• Galactic-Field IMFs of Massive Stars
• Evidence for a fundamental stellar upper mass limit from clustered star formation
• Cluster Mass Functions in the Large and Small Magellanic Clouds: Fading and Size of Sample Effects
• The Luminosity Function of Star Clusters in Spiral Galaxies
• Implications for the formation of star clusters from extra-galactic star-formation rates
• On the Mass-to-Light ratio and the Initial Mass Function in disc galaxies
• The Predicted Metallicity Distribution of Stars in Dwarf Spheroidal Galaxies
• On the universal outcome of star-formation: Is there a link between stars and brown-dwarfs?
• The Pleiades mass function: models versus observations

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