The Stellar Mass Distribution in the Giant Star Forming Region NGC 346

TL;DR

This study analyzes the present day mass function of NGC 346 in the SMC using Hubble data, finding a Salpeter-like slope and evidence of primordial mass segregation, suggesting a universal IMF unaffected by environment.

Contribution

First detailed PDMF measurement of NGC 346, revealing a Salpeter-like slope and primordial mass segregation in a young star cluster in the SMC.

Findings

PDMF slope of -1.43±0.18 in 0.8-60 M☉ range

Mass segregation likely primordial due to young age (~3 Myr)

IMF appears universal across different environments

Abstract

Deep F555W and F814W Hubble Space Telescope ACS images are the basis for a study of the present day mass function (PDMF) of NGC346, the largest active star forming region in the Small Magellanic Cloud (SMC). We find a PDMF slope of Gamma=-1.43+/-0.18 in the mass range 0.8-60 Mo, in excellent agreement with the Salpeter Initial Mass Function (IMF) in the solar neighborhood. Caveats on the conversion of the PDMF to the IMF are discussed. The PDMF slope changes, as a function of the radial distance from the center of the NGC 346 star cluster, indicating a segregation of the most massive stars. This segregation is likely primordial considering the young age (~3 Myr) of NGC346, and its clumpy structure which suggests that the cluster has likely not had sufficient time to relax. Comparing our results for NGC346 with those derived for other star clusters in the SMC and the Milky Way (MW), we conclude that, while the star formation process might depend on the local cloud conditions, the IMF does not seem to be affected by general environmental effects such as galaxy type, metallicity, and dust content.