A Galactic Self-Portrait: 3D density map and integrated properties of the Milky Way
Julie Imig, NMSU
The Milky Way Galaxy, our home, is the ideal laboratory for studying galaxy formation and evolution. The star formation history and chemical evolution of the Milky Way disk is imprinted in the ages, phase-space information, and chemical compositions of individually resolved stars. Large-scale spectroscopic surveys like the Apache Point Observatory Galactic Evolution Experiment (APOGEE) have observed hundreds of thousands of Milky Way stars in unprecedented detail, and the resulting wealth of information has placed strong constraints on the structure and evolution history of the Milky Way. However, direct comparison between the Milky Way and the broader population of disk galaxies in the Universe remains a challenge. In extragalactic astronomy, galaxies are observed in integrated light; the cumulative contribution of millions of stars at once. The inside perspective we have of the Milky Way complicates our ability to directly compare the Milky Way to other spiral galaxies. In this project, we will reconstruct an external view of the Milky Way, creating a Galactic “self-portrait” to close the observational gap between Galactic and extragalactic astronomy. The final data release of the APOGEE survey will be used to model a three dimensional density map of the Milky Way disk, as a function of stellar ages, metallicity, and alpha-element abundances. This detailed density map will provide strong new constraints on the global properties of the Milky Way, including scale lengths, metallicity gradients, and integrated colors across different stellar populations. Finally, we will combine this comprehensive map of the Galactic disk with simple stellar population models created from the MaStar stellar library to create an integrated light spectrum of the Milky Way Galaxy. This spectrum will be compared to the spectra of both simulated and observed Milky Way analog galaxies to explore how the various behaviors of stellar populations manifest in integrated light. This holistic picture of the Milky Way will facilitate a direct comparison between our Galaxy and the broader population of disk galaxies in the Universe.