Modeling Substructure in the Milky Way Galaxy
Abstract
We model substructure in the Milky Way halo using data taken from the five fields of the Deep Lens Survey (DLS). We select DLS objects that are consistent with the PSF to create color-magnitude Hess diagrams for each field. We observe significant substructure in at least two out of the five fields. To enhance the visibility of the substructure, we model and subtract the population of unresolved background galaxies, and subtract a smooth model of the Milky Way halo. This halo model is constructed by remapping the observed Hess diagram of stars in DLS Field 5 (F5), which has a smooth appearance. We use colors and absolute magnitudes from the Yonsei-Yale isochrones to create a map of distance modulus for main sequence stars in color-magnitude space for each DLS field. An Einasto model of the galaxy is used to predict the model density ratio of stars in each field as a function of distance modulus. The F5 Hess diagram is then multiplied by the model density ratio maps for F1 - F4 to yield semi-empirical model Hess diagrams. Subtracting these models from the observed Hess diagrams emphasizes the substructure of a given field. We fit simple models to the residual substructure in each DLS field using a Gaussian with three free parameters: distance of enhancement, depth along the LOS, and amplitude (i.e. strength). We discuss the use of this galaxy substructure model in calculating the overall density profile of the Milky Way.
- Publication:
-
American Astronomical Society Meeting Abstracts #221
- Pub Date:
- January 2013
- Bibcode:
- 2013AAS...22125424G