Haffner 16: A young moving group in the making

The photometric properties of main sequence (MS) and pre-main sequence (PMS) stars in the young cluster Haffner 16 are examined using images recorded with the Gemini South Adaptive Optics Imager (GSAOI) and corrected for atmospheric blurring by the Gemini Multi-Conjugate Adapative Optics System (GeMS). A rich population of PMS stars is identified, and comparisons with isochrones suggest an age ≲10 Myr, assuming a distance modulus of 13.5 (D = 5 kpc). This age is consistent with that estimated from the lower cutoff of the MS on the K-band luminosity function and is ~2 Myr younger than the age found from bright MS stars at visible wavelengths. When compared with the solar neighborhood, Haffner 16 is roughly a factor of 2 deficient in objects with subsolar masses. PMS objects in the cluster are also more uniformly distributed on the sky than bright MS stars. It is suggested that Haffner 16 is dynamically evolved and that it is shedding protostars with subsolar masses. Young low mass clusters like Haffner 16 are one possible source of PMS stars in the field. The cluster will probably evolve on time scales of ~100-1000 Myr into a diffuse moving group with a mass function that is very different from that which prevailed early in its life.