Towards a fully consistent Milky Way disc model - III. Constraining the initial mass function

TL;DR

This paper develops a new, observationally supported initial mass function (IMF) for the Milky Way's disc, derived through forward modeling and comparison with stellar data, refining our understanding of star formation.

Contribution

It introduces a new IMF constrained by local stellar observations using a forward modeling approach, improving the accuracy of Milky Way disc models.

Findings

The IMF is a two-slope broken power law from 0.5 to 10 Msun.

Break at 1.39 Msun with slopes -1.49 and -3.02.

Consistent results with the Besancon group validate the modeling technique.

Abstract

We use our vertical Milky Way disc model together with Galaxia to create mock observations of stellar samples in the solar neighbourhood. We compare these to the corresponding volume complete observational samples of dereddened and binary accounted data from Hipparcos and the Catalogue of Nearby Stars. Sampling the likelihood in the parameter space we determine a new fiducial IMF considering constraints from dwarf and giant stars. The resulting IMF observationally backed in the range from 0.5 to 10 Msun is a two slope broken power law with -1.49 +- 0.08 for the low mass slope, a break at 1.39 +- 0.05 Msun and a high mass slope of -3.02 +- 0.06. The Besancon group also converging to a similar IMF even though their observational sample being quite different to ours shows that the forward modelling technique is a powerful diagnostic to test theoretical concepts like the local field star IMF.