Measuring the Initial Mass Function of Low Mass Stars and Brown Dwarfs

TL;DR

This paper reviews methods and challenges in determining the initial mass function for low-mass stars and brown dwarfs, highlighting uncertainties and discrepancies across different environments and observational approaches.

Contribution

It critically assesses current methodologies and uncertainties in measuring the low-mass initial mass function in various stellar populations.

Findings

Field and young cluster IMFs may be similar but uncertainties remain.

Some cluster IMFs are significantly different, indicating variability.

Brown dwarf IMFs in different environments are not yet consistent.

Abstract

I review efforts to determine the form and any lower limit to the initial mass function in the Galactic disk, using observations of low-mass stars and brown dwarfs in the field, young clusters and star forming regions. I focus on the methodologies that have been used and the uncertainties that exist due to observational limitations and to systematic uncertainties in calibrations and theoretical models. I conclude that whilst it is possible that the low-mass IMFs deduced from the field and most young clusters are similar, there are too many problems to be sure; there are examples of low-mass cluster IMFs that appear to be very discrepant and the IMFs for brown dwarfs in the field and young clusters have yet to be reconciled convincingly.