GeMS in the Outer Galaxy: Near-Infrared Imaging of Three Young Clusters at Large Galactic Radii

Abstract: Images recorded with the Gemini South Adaptive Optics Imager (GSAOI) and corrected for atmospheric seeing by the Gemini Multiconjugate Adaptive Optics System (GeMS) are used to investigate the stellar contents of the young outer Galactic disk clusters Haffner 17, NGC 2401, and NGC 3105. Ages estimated from the faint end of the main sequence (MS) and the ridgeline of the pre-main sequence (PMS) on the (K, J-K) color-magnitude diagrams are consistent with published values that are based on the MS turn-off, with the GSAOI data favoring the younger end of the age range for NGC 2401 in the literature. The mass function (MF) of NGC 2401 is similar to that in the Solar neighborhood, and stars spanning a wide range of masses in this cluster have similar clustering properties on the sky. It is concluded that NGC 2401 is not evolved dynamically. In contrast, the MF of Haffner 17 differs significantly from that in the Solar neighborhood over all masses covered by these data, while the MF of NGC 3105 is deficient in objects with sub-solar masses when compared with the Solar neighborhood. Low mass objects in Haffner 17 and NGC 3105 are also more uniformly distributed on the sky than brighter, more massive, MS stars. This is consistent with both clusters having experienced significant dynamical evolution.