Understanding the formation history of the Milky Way disk using Copulas and Elicitable Maps

Oregon Convention Center 

In the Milky Way, the distribution of stars in the chemistry vs. age planes holds essential information about the formation history of its disk. I investigate these planes by applying novel statistical methods called copulas and elicitable maps to the ages and chemical compositions of stars in the APOGEE survey. I find that the two populations of stars in the disk, the low- and high-α sequences, have a clean separation in copula space. Using this space, I provide an automated separation of the α sequences using a purely statistical approach. This separation supports that the high- and low-α sequences formed sequentially as opposed to having a continuous star formation history. I then combine copulas with elicitable maps to precisely obtain the correlation between stellar age and metallicity (iron composition) conditional on radius and height in the disk. The resulting trends in the age-metallicity correlation with radius, height, and [α/Fe] are consistent with the effects of strong spiral-driven migration of stars across radii in the disk.

In this talk, I will discuss my statistical methods, their application, and the implications of my results for understanding the Milky Way.