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.
Spatially Resolved Galaxy Interactions
Jorge Moreno, Pomona College
The focus of this talk is to address the spatial structure and evolution of star formation and the interstellar medium ISM in interacting galaxies. We use an extensive suite of parsec-scale galaxy merger simulations, which employs the “Feedback In Realistic Environments” model FIRE-2. This framework resolves star formation, feedback processes, and the multi-phase structure of the ISM. We focus on the galaxy-pair stages of interaction. We find that close encounters substantially augment cool HI and cold-dense H2 gas budgets, elevating the formation of new stars as a result. We also find that galaxies with elevated global star formation rate SFR experience intense nuclear SFR enhancement, driven by high levels of either star formation efficiency SFE or available cold-dense gas fuel. Galaxies with suppressed global SFR also contain a nuclear cold-dense gas reservoir, but low SFE levels diminish SFR in the central region. Our numerical predictions underscore the need of substantially larger, and/or merger-dedicated, spatially-resolved integral-field spectroscopic galaxy surveys — capable of examining vast and diverse samples of interacting systems — coupled with multi-wavelength campaigns aimed to capture their internal ISM structure. If time allows, I will also speak of dark matter free dwarf galaxies in FIREBox, a cosmological simulation of galaxy formation with FIRE. https://arxiv.org/abs/2009.11289