Southern infrared proper motion survey - III. Constraining the mass function of low mass stars

The stellarmass function is one of the fundamental distributions of stellar astrophysics. Its form at masses similar to the Sun was found by Salpeter (1955, ApJ, 121, 161) to be a power-law m(-alpha) with a slope of alpha = 1.35. Since then the mass function in the field, in stellar clusters and in other galaxies has been studied to identify variation due to environment and mass range. Here we use results from previous papers in the SIPS series to constrain the mass function of low mass stars (0.075 M-circle dot < m < 0.2 M (circle dot)). We use simulations of the local low mass stellar population to model the results of the SIPS-II survey. We then vary the input parameters of these simulations (the exponent of the mass function alpha and a stellar birthrate parameter beta) and compare the simulated survey results with those from the actual survey. After a correction for binarity and taking into account potential errors in our model we find that alpha = -0.62 9 +/- 0.26 for the quoted mass range.