Massive star clusters NGC 419 and NGC 1846

We have obtained more than one hundred high-resolution stellar spectra in and around each cluster using the multi-object spectrograph M2FS on the Magellan/Clay Telescope. Line-of-sight velocities and positions of the stars observed in each cluster were used as input to an expectation-maximization algorithm used to estimate cluster membership probabilities, resulting in samples of 46 and 52 likely members (P_M_>=50 per cent) in NGC 419 and NGC 1846, respectively.

This process employed single-mass King models constrained by the structural parameters of the clusters and provided self-consistent dynamical mass estimates for both clusters. Our best-fitting results show that NGC 419 has a projected central velocity dispersion of 2.44^+0.37^_-0.21_km/s, corresponding to a total mass of 7.6^+2.5^_-1.3_x10^4^M_{sun}_ and V-band M/L ratio of 0.22^+0.08^_-0.05_ in solar units. For NGC 1846, the corresponding results are 2.04^+0.28^_-0.24_km/s, 5.4^+1.5^_-1.4_x10^4^M_{sun}_, and 0.32^+0.11^_-0.11_.