54 citations · 161 across the 17 of their papers we have counts for
12 papers · 1 filter
A Broken Clock Is Right Twice a Day: [Ce/Mg] Is Not a Universal Chemical Clock
Liam O. Dubay, Jennifer A. Johnson, James W. Johnson +14
The ratio of -process to -element enrichment () has been proposed as a ``chemical clock,'' or a means to estimate stellar ages. However, the age-- relation vari…
The galactic chemical evolution of carbon: Implications for stellar nucleosynthesis
Daniel A. Boyea, James W. Johnson, David H. Weinberg
Carbon (C) is thought to be produced by both core collapse supernovae (CCSN) and asymptotic giant branch (AGB) stars, but the relative contributions of these two sources are uncert…
Metals versus Non-metals: Chemical Evolution of Hydrogen and Helium Isotopes in the Milky Way
James W. Johnson, Miqaela K. Weller, Ryan J. Cooke
Star formation drives changes in the compositions of galaxies, fusing H and He into heavier nuclei. This paper investigates the differences in abundance evolution between metal and…
Constraints on Radial Gas Flows in the Milky Way Disk Revealed by Large Stellar Age Catalogs
James W. Johnson
Disk galaxies like the Milky Way are expected to experience gas flows carrying matter toward their centers. This paper investigates the role of these radial gas flows in models of…
Challenges to the Two-Infall Scenario by Large Stellar Age Catalogs
Liam O. Dubay, Jennifer A. Johnson, James W. Johnson +1
Stars in the Milky Way disk exhibit a clear separation into two chemically distinct populations based on their [/Fe] ratios. This -bimodality is not a universal feature of si…
Many elements matter: Detailed abundance patterns reveal star-formation and enrichment differences among Milky Way structural components
Emily J. Griffith, David W. Hogg, Sten Hasselquist +5
Many nucleosynthetic channels create the elements, but two-parameter models characterized by and Fe nonetheless predict stellar abundances in the Galactic disk to accuracies of…
The Milky Way Radial Metallicity Gradient as an Equilibrium Phenomenon: Why Old Stars are Metal-Rich
James W. Johnson, David H. Weinberg, Guillermo A. Blanc +12
Metallicities of both gas and stars decline toward large radii in spiral galaxies, a trend known as the radial metallicity gradient. We quantify the evolution of the metallicity gr…
Rising from the Ashes II: The Bar-driven Abundance Bimodality of the Milky Way
Angus Beane, James Johnson, Vadim Semenov +3
The Milky Way hosts at least two modes in its present day distribution of Fe and alpha-elements. The exact cause of this bimodality is disputed, but one class of explanations invol…
The APO-K2 Catalog. II. Accurate Stellar Ages for Red Giant Branch Stars across the Milky Way
Jack T. Warfield, Joel C. Zinn, Jessica Schonhut-Stasik +11
We present stellar age determinations for 4661 red giant branch stars in the APO-K2 catalog, derived using mass estimates from K2 asteroseismology from the K2 Galactic Archaeology…
Modeling the Galactic Chemical Evolution of Helium
Miqaela K. Weller, David H. Weinberg, James W. Johnson
We examine the galactic chemical evolution (GCE) of He in one-zone and multi-zone models, with particular attention to theoretical predictions and empirical constraints on IMF-…
Galactic Chemical Evolution Models Favor an Extended Type Ia Supernova Delay-Time Distribution
Liam O. Dubay, Jennifer A. Johnson, James W. Johnson
Type Ia supernovae (SNe Ia) produce most of the Fe-peak elements in the Universe and therefore are a crucial ingredient in galactic chemical evolution models. SNe Ia do not explode…
The Scale of Stellar Yields: Implications of the Measured Mean Iron Yield of Core Collapse Supernovae
David H. Weinberg, Emily J. Griffith, James W. Johnson +1
The scale of alpha-element yields is difficult to predict from theory because of uncertainties in massive star evolution, supernova physics, and black hole formation, and it is dif…