We use deep Hubble Space Telescope photometry of the rich , young ( \sim 20–45 Myr-old ) star cluster NGC 1818 in the Large Magellanic Cloud to derive its stellar mass function ( MF ) down to \sim 0.15 M _ { \odot } .
This represents the deepest robust MF thus far obtained for a stellar system in an extragalactic , low-metallicity ( [ Fe/H ] \simeq - 0.4 dex ) environment .
Combining our results with the published MF for masses above 1.0 M _ { \odot } , we obtain a complete present-day MF .
This is a good representation of the cluster ’ s initial MF ( IMF ) , particularly at low masses , because our observations are centred on the cluster ’ s uncrowded half-mass radius .
Therefore , stellar and dynamical evolution of the cluster will not have affected the low-mass stars significantly .
The NGC 1818 IMF is well described by both a lognormal and a broken power-law distribution with slopes of \Gamma = 0.46 \pm 0.10 and \Gamma \simeq - 1.35 ( Salpeter-like ) for masses in the range from 0.15 to 0.8 M _ { \odot } and greater than 0.8 M _ { \odot } , respectively .
Within the uncertainties , the NGC 1818 IMF is fully consistent with both the Kroupa solar-neighbourhood and the Chabrier lognormal mass distributions .