The Mass Function of omega Centauri down to 0.15 M_s

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.

9 pages, 10 figures, accepted for publication by MNRAS

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• The non-peculiar velocity dispersion profile of the stellar system omega Centauri
• Evolution of second generation stars in stellar disks of globular and nuclear clusters: Omega Centauri as a test case
• The Origin of the Stellar Mass Distribution and Multiplicity
• The stellar Initial Mass Function of the solar neighbourhood revealed by Gaia
• The non-segregated population of blue straggler stars in the remote globular cluster Palomar 14
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• Mass segregation in the outer halo globular cluster Palomar 14
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• The not so simple stellar system Omega Cen. II. Evidence in support of a merging scenario
• A stellar census in globular clusters with MUSE. A new perspective on the multiple main sequences of $\omega$ Centauri
• Stellar collisions in globular clusters: Constraints on the initial mass function of the first generation of stars
• Exploring the Mass Segregation Effect of X-ray Sources in Globular Clusters. IV. Evidence of Black Hole Burning in $\omega$ Centauri
• New Way to Date Globular Clusters: Brown Dwarf Cooling Sequences