Authors: Sebastian Kamann, Nathan J. Bastian, Tim-Oliver Husser, Silvia Martocchia, Christopher Usher, Mark den Brok, Stefan Dreizler, Andreas Kelz, Davor Krajnović, Johan Richard, Matthias Steinmetz, Peter M. Weilbacher
Abstract: We present adaptive optics (AO) assisted integral-field spectroscopy of the intermediate-age star cluster NGC 419 in the Small Magellanic Cloud. By investigating the cluster dynamics and the rotation properties of main sequence turn-off stars (MSTO), we demonstrate the power of AO-fed MUSE observations for this class of objects. Based on 1 049 radial velocity measurements, we determine a dynamical cluster mass of 1.4+/-0.2x10^5 M_sun and a dynamical mass-to-light ratio of 0.67+/-0.08, marginally higher than simple stellar population predictions for a Kroupa initial mass function. A stacking analysis of spectra at both sides of the extended MSTO reveals significant rotational broadening. Our analysis further provides tentative evidence that red MSTO stars rotate faster than their blue counterparts. We find average V sin i values of 87+/-16 km/s and 130+/-22 km/s for blue and red MSTO stars, respectively. Potential systematic effects due to the low spectral resolution of MUSE can reach 30 km/s but the difference in V sin i between the populations is unlikely to be affected.
My Comment: The first two "research" assignments I ever had in graduate school involved star clusters and cluster dynamics. This was a bit perplexing as I was looking to work on solar system dynamics, and only knew that a "cluster" was a group of gravitationally bound stars from reading through an introductory astronomy text prior to being a TA; the only serious astronomy I had done as an undergrad was to work out the transformations of taking earth-based observations into orbits.
My Scrawling Notes:
