Star clusters cluster mass distribution function

Fig. 1. Mean Li abundance as a function of age. Li abundances are in the usual notation log n(Li)= N(Li)/N(H)+12. Different symbols indicate stars in different mass bins, namely 1 0.02 M0 (circles), 1.05 0.02 M0 (squares) and 1.1 0.02 M0 (triangles). The Sun is also shown. The horizontal line denotes the initial log n(Li). The following clusters have been considered 120 Myr Pleiades 600 Myr Hyades 2 Gyr IC 4651, NGC 3680, NGC 752 4.5 Gyr M 67 (only the upper envelope of the Li vs. Teff distribution -see text) 7 Gyr NGC 188. The cluster samples have all been analysed with the same method. Error bars correspond to lcr deviations from the mean.

The distribution function for field stars in the halo is reasonably well fitted by the Simple model equation (8.20) with a small remaining gas fraction, but with a very low effective yield p 10-11Z for oxygen (see earlier comments on dwarf galaxies). This was first noted (actually for globular clusters) by Hartwick (1976), who pointed out that it could be readily explained by continuous loss of gas from the halo in the form of a homogeneous wind with a mass loss rate from the system proportional to the rate of star formation. In this case,... 

The basic data for stochastic simulations of galaxies and their constituent populations and metallicity evolution is the initial mass function (IMF), which represents the mass distribution with which stars are presumed to form. Its derivation from the observed distribution of luminosity among field stars (refs. 57 and 58 and references therein) and from star clusters involves many detailed corrections for both stellar evolution and abundance variations among the observed population. The methods for achieving the IMF from the observed distribution are most thoroughly outlined by Miller and Scalo but can be stated briefly, since they also relate to an accurate testing of various proposed stochastic methods. It should first be noted that the problems encountered for stellar distributions are quite similar to those with which studies of galaxies and thdr intrinsic properties have to deal. 

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