科研之友
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摘要
We derive a semi-empirical galactic initial mass IMF) from observational constraints. We assume that the IMF, psi(m), is a smooth function of the stellar mass m. The mass dependence of the proposed IMF is determined by five parameters: the low-mass slope gamma, the high-mass slope -Gamma (taken to be -1.35), the characteristic mass m(ch) (similar to the peak mass of the IMF), and the lower and upper limits on the mass, m(l) and m(u) (taken to be 0.004 and 120 M-circle dot, respectively): psi(m)d ln m alpha m(-Gamma) {1 - exp[-(m/m(ch))(gamma+Gamma)]}d ln m. The values of gamma and m(ch) are derived from two integral constraints: (1) the ratio of the number density of stars in the range m = 0.1-0.6M(circle dot) to that in the range m = 0.6-0.8 M-circle dot as inferred from the mass distribution of field stars in the local neighborhood and (2) the ratio of the number of stars in the range m = 0.08-1 M-circle dot to the number of brown dwarfs in the range m = 0.03-0.08 M-circle dot in young clusters. The IMF satisfying the above constraints is characterized by the parameters gamma = 0.51 and m(ch) = 0.35 M-circle dot (which corresponds to a peak mass of 0.27 M-circle dot). This IMF agrees quite well with the Chabrier IMF for the entire mass range over which we have compared with data, but predicts significantly more stars with masses <0.03 M-circle dot; we also compare with other IMFs in current use and give a number of important parameters implied by the IMFs.
- 出版日期2011-1
