The Mass Function of omega Centauri down to 0.15 M_s

TL;DR

This study measures the mass function of omega Centauri down to 0.15 solar masses using deep observations, revealing a broken power-law shape that closely approximates the initial mass function of the cluster.

Contribution

First detailed measurement of omega Centauri's low-mass stellar mass function down to 0.15 M_s, providing insights into its initial mass function unaffected by dynamical evolution.

Findings

Mass function well fitted by broken power-law with slopes -2.3 and -0.8

Mass function extends down to 0.15 M_s

Possible primordial differences in low-mass MF slopes among globular clusters

Abstract

By means of deep FORS1@VLT and ACS@HST observations of a wide area in the stellar system omega Cen we measured the luminosity function of main sequence stars down to R=22.6 and I_{F814W}=24.5 . The luminosity functions obtained have been converted into mass functions and compared with analytical Initial Mass Functions (IMFs) available in the literature. The mass function obtained, reaching M~0.15 M_s, can be well reproduced by a broken power-law with indices alpha=-2.3 for M>0.5 M_s and alpha=-0.8 for M<0.5 M_s. Since the stellar populations of omega Cen have been proved to be actually unaffected by dynamical evolution processes, the mass function measured in this stellar system should represent the best approximation of the IMF of a star cluster. The comparison with the MF measured in other Galactic globular clusters suggests that possible primordial differences in the slope of the low-mass end of their MF could exist.