Dynamical Structure of the Quintuplet Cluster
I am currently working alongside Jessica Lu and Matthew Hosek, Jr. on a proper motion study of the Quintuplet cluster, a so-called young massive cluster that’s really close to the center of the galaxy. Along with the Arches cluster and the Young Nuclear Cluster, the Quintuplet cluster is one of the only examples of such a cluster within such tight proximity to the central super-massive black hole.
I’m currently interested in the structure of the Quintuplet cluster. Because of its location in an extreme tidal environment, it is very likely that we would see signs of disruption or other footprints of structural deformation that would be absent from other clusters. In addition, because the Quintuplet cluster is largely thought to be older than the Arches cluster, the former is often viewed as an older version of the latter. Using previous work on the Arches cluster, we will be able to compare the clusters’ structures directly.
While its pretty clear from the image that there is, indeed, a cluster there, it is not altogether clear which stars are actually in the cluster. Some stars may be in front of the cluster and some stars may be behind. While there are many ways of doing this, a fairly robust way is to watch the stars over several years and to see which ones move together. The stars that aren’t in the cluster tend to have a high spread in motions, and the cluster is fairly distinguishable in proper motion space. We use the Hubble Space Telescope WFC3 IR camera to make four observations over six years for this purpose.
Once this is done, we correct for the wavelength-dependent scattering of light, or extinction, as well as a bias for brighter stars to be detected over fainter stars, or completeness. We can then construct a radial profile (also called a “surface density profile”), the 2D density of stars as a function of distance from the center of the cluster. We can also examine structural features like mass segregation, the tendency of more massive stars to appear at smaller radii in the cluster, and a possible tidal tail, which would manifest in an elongation in the cluster’s direction of motion.