"Chemical evolution of the Milky Way discs: providing stronger constraints from observations"
Fiorenzo Vincenzo (OSU Physics)
The observed [alpha/Fe]-[Fe/H] diagram is a powerful diagnostic of the star-formation history and stellar nucleosynthesis in galaxies; it can be thought of as an analogue of the color-magnitude diagram, which makes use of the chemical abundances in the stellar photosphere instead of the photometric properties of the stars. In this talk I will show the results of a new model developed to fit the distribution of stars on the Milky Way disc from SDSS-IV APOGEE-2 DR16 observations, by considering how stars (mostly red giants) distribute in the two-dimensional space determined by their [alpha/Fe] abundance ratio and vertical height, for different [Fe/H] and Galactocentric distances on the Milky Way disc. Our formalism makes use of a likelihood analysis, accounting for the biases introduced by the assumed selection in effective temperature and surface gravity, and the different vertical distributions of thick- and thin-disc stars. This analysis -- which will provide intrinsic chemical abundance distributions cleaned from the main selection effects -- will help to put stronger constraint on various physical and dynamical processes that may have shaped the secular evolution of the disc of the Milky Way, like stellar migrations and gas/metal flows. For this reason, I will try to frame the results of this analysis in the context of the predictions of a cosmological hydrodynamical simulation for the Milky Way, that I have published earlier this year (Vincenzo & Kobayashi, 2020, MNRAS, 496, 80).
"Cosmology from Redshift Surveys: Results from the completed SDSS IV eBOSS dataset and looking forward to DESI"
Ashley Ross (OSU Physics)
The completion of the extended Baryon Oscillation Spectroscopic Survey (eBOSS) marks the culmination of two decades of SDSS mapping the 3D large-scale structure of the Universe. I will describe these maps, comprised of galaxies, quasars, and Lyman-alpha forests, and how we compress the information they contain into distances, from the baryon acoustic oscillation feature, and the rate of structure growth, from redshift-space distortions. I will then describe the cosmological implications of these data, both on their own and in combination with other experiments. The Dark Energy Spectroscopic Instrument (DESI) represents the next generation. It will collect 10x the number of redshifts as SDSS. I will provide an update on its status and place its forecasted results in the context of our current results (from SDSS++).