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Chemical Cartography with APOGEE : Multi-element Abundance Ratios

Weinberg, David H.; Holtzman, Jon A. LU ; Hasselquist, Sten; Bird, Jonathan C.; Johnson, Jennifer A.; Shetrone, Matthew; Sobeck, Jennifer; Allende Prieto, Carlos; Bizyaev, Dmitry and Carrera, Ricardo, et al. (2019) In Astrophysical Journal 874(1).
Abstract

We map the trends of elemental abundance ratios across the Galactic disk, spanning R = 3-15 kpc and midplane distance |Z| = 0-2 kpc, for 15 elements in a sample of 20,485 stars measured by the SDSS/APOGEE survey (O, Na, Mg, Al, Si, P, S, K, Ca, V, Cr, Mn, Fe, Co, Ni). Adopting Mg rather than Fe as our reference element, and separating stars into two populations based on [Fe/Mg], we find that the median trends of [X/Mg] versus [Mg/H] in each population are nearly independent of location in the Galaxy. The full multi-element cartography can be summarized by combining these nearly universal median sequences with our measured metallicity distribution functions and the relative proportions of the low-[Fe/Mg] (high-α) and high-[Fe/Mg] (low-α)... (More)

We map the trends of elemental abundance ratios across the Galactic disk, spanning R = 3-15 kpc and midplane distance |Z| = 0-2 kpc, for 15 elements in a sample of 20,485 stars measured by the SDSS/APOGEE survey (O, Na, Mg, Al, Si, P, S, K, Ca, V, Cr, Mn, Fe, Co, Ni). Adopting Mg rather than Fe as our reference element, and separating stars into two populations based on [Fe/Mg], we find that the median trends of [X/Mg] versus [Mg/H] in each population are nearly independent of location in the Galaxy. The full multi-element cartography can be summarized by combining these nearly universal median sequences with our measured metallicity distribution functions and the relative proportions of the low-[Fe/Mg] (high-α) and high-[Fe/Mg] (low-α) populations, which depend strongly on R and |Z|. We interpret the median sequences with a semi-empirical two-process model that describes both the ratio of core collapse and Type Ia supernova (SN Ia) contributions to each element and the metallicity dependence of the supernova yields. These observationally inferred trends can provide strong tests of supernova nucleosynthesis calculations. Our results lead to a relatively simple picture of abundance ratio variations in the Milky Way, in which the trends at any location can be described as the sum of two components with relative contributions that change systematically and smoothly across the Galaxy. Deviations from this picture and future extensions to other elements can provide further insights into the physics of stellar nucleosynthesis and unusual events in the Galaxys history.

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@article{cdaf3491-5fa5-4575-99ca-7f5cac44dc30,
  abstract     = {<p>We map the trends of elemental abundance ratios across the Galactic disk, spanning R = 3-15 kpc and midplane distance |Z| = 0-2 kpc, for 15 elements in a sample of 20,485 stars measured by the SDSS/APOGEE survey (O, Na, Mg, Al, Si, P, S, K, Ca, V, Cr, Mn, Fe, Co, Ni). Adopting Mg rather than Fe as our reference element, and separating stars into two populations based on [Fe/Mg], we find that the median trends of [X/Mg] versus [Mg/H] in each population are nearly independent of location in the Galaxy. The full multi-element cartography can be summarized by combining these nearly universal median sequences with our measured metallicity distribution functions and the relative proportions of the low-[Fe/Mg] (high-α) and high-[Fe/Mg] (low-α) populations, which depend strongly on R and |Z|. We interpret the median sequences with a semi-empirical two-process model that describes both the ratio of core collapse and Type Ia supernova (SN Ia) contributions to each element and the metallicity dependence of the supernova yields. These observationally inferred trends can provide strong tests of supernova nucleosynthesis calculations. Our results lead to a relatively simple picture of abundance ratio variations in the Milky Way, in which the trends at any location can be described as the sum of two components with relative contributions that change systematically and smoothly across the Galaxy. Deviations from this picture and future extensions to other elements can provide further insights into the physics of stellar nucleosynthesis and unusual events in the Galaxys history.</p>},
  articleno    = {102},
  author       = {Weinberg, David H. and Holtzman, Jon A. and Hasselquist, Sten and Bird, Jonathan C. and Johnson, Jennifer A. and Shetrone, Matthew and Sobeck, Jennifer and Allende Prieto, Carlos and Bizyaev, Dmitry and Carrera, Ricardo and Cohen, Roger E. and Cunha, Katia and Ebelke, Garrett and Fernandez-Trincado, J. G. and Garcia-Hernández, D. A. and Hayes, Christian R. and Jönsson, Henrik and Lane, Richard R. and Majewski, Steven R. and Malanushenko, Viktor and Mészáros, Szabolcs and Nidever, David L. and Nitschelm, Christian and Pan, Kaike and Rix, Hans Walter and Rybizki, Jan and Schiavon, Ricardo P. and Schneider, Donald P. and Wilson, John C. and Zamora, Olga},
  issn         = {0004-637X},
  keyword      = {Galaxy: abundances,Galaxy: disk,nuclear reactions, nucleosynthesis, abundances,stars: abundances},
  language     = {eng},
  month        = {03},
  number       = {1},
  publisher    = {American Astronomical Society},
  series       = {Astrophysical Journal},
  title        = {Chemical Cartography with APOGEE : Multi-element Abundance Ratios},
  url          = {http://dx.doi.org/10.3847/1538-4357/ab07c7},
  volume       = {874},
  year         = {2019},
}