Dynamically Tagged Groups of Carbon-Enhanced Metal-Poor Stars from the AEGIS Survey

Data from the Southern Hemisphere’s AAOmega Evolution of Galactic Structure (AEGIS) spectroscopic survey are used to estimate dynamical parameters for stars selected from ­­an initial sample of 3550 carbon-enhanced metal-poor (CEMP) stars. With about 1500 stars in this sample for which sufficient kinematic data are available through GAIA Data Release 2 measurements of proper motions, Bayesian StarHorse distances based on Gaia parallaxes and radial velocities from the AEGIS spectra, we derive their dynamical parameters with the code Action-based Galaxy Modelling Architecture (AGAMA). The resulting energies and orbital actions (E, J_r, J_φ, J_z) are clustered in dynamical space using the Hierarchical Density-Based Spatial Clustering of Applications with Noise (HDBSCAN) algorithm to identify Dynamically Tagged Groups (DTGs). We consider the dispersions in the abundances of [Fe/H], [C/Fe] and [α/Fe], along with the CEMP class, in order to test the significance of their association with parent dwarf galaxies (and possibly globular clusters) disrupted into the Galactic halo. This work received partial support from grant PHY 14-30152; Physics Frontier Center/ JINA Center for the Evolution of the Elements (JINA-CEE), awarded by the U.S. National Science Foundation.