The very low-mass stellar content of the young supermassive Galactic star cluster Westerlund 1

Understand

We present deep near-infrared HST/WFC3 observations of the young supermassive Galactic star cluster Westerlund 1 and an adjacent control field.

• The depth of the data is sufficient to derive the mass function for the cluster as a function of radius down to 0.15 M$_\odot$ in the outer parts of the cluster.
• We identify for the first time a flattening in the mass function (in logarithmic units) at a mass range that is consistent with that of the field and nearby embedded clusters.
• Through log-normal functional fits to the mass functions we find the nominal peak mass to be comparable to that of the field and nearby embedded star clusters.