On the mass range of the first stars

The physical origins of the initial stellar mass function (IMF) are discussed. Observational evidence is summarized which suggests that the mass range of the first stars extended over a range of 10-100 solar masses and perhaps up to several hundred solar masses. Processes which may have determined the IMF of the first stars from precursor clouds initially uniform on stellar mass scales are discussed. The difficulties facing the process called opacity-limited gravitational fragmentation are discussed, and it is argued that the stellar IMF puzzle can be solved by considering the thermochemical stability of clouds of primordial abundance. These clouds were thermally unstable, with exponential growth of fluctuations over well-defined mass scales. Molecular hydrogen formed rapidly and cooling followed, resulting in the formation of small clumps which aggregated during the cloud collapse, forming a nearly flat spectrum of bound clumps extending from about 0.1 solar mass to about 100 solar masses. These may be identified with the first stars.