Using chemical tagging to redefine the interface of the Galactic disc and halo

By K. Hawkins, Paulina Jofré, T. Masseron, G. Gilmore. 2015

135 citations recorded by the source corpus.

We present a chemical abundance distribution study in 14 $\alpha$, odd-Z, even-Z, light, and Fe-peak elements of approximately 3200 intermediate metallicity giant stars from the APOGEE survey. The main aim of our analysis is to explore the Galactic disk-halo transition region between -1.20 $<$ [Fe/H] $<$ -0.55 as a means to study chemical difference (and similarities) between these components. In this paper, we show that there is an $\alpha$-poor and $\alpha$-rich sequence within both the metal-poor and intermediate metallicity regions. Using the Galactic rest-frame radial velocity and spatial positions, we further separate our sample into the canonical Galactic components. We then studied the abundances ratios, of Mg, Ti, Si, Ca, O, S, Al, C+N, Na, Ni, Mn, V, and K for each of the components and found the following: (1) the $\alpha$-poor halo subgroup is chemically distinct in the $\alpha$-elements (particularly O, Mg, and S), Al, C+N, and Ni from the $\alpha$-rich halo, consistent with the literature confirming the existence of an $\alpha$-poor accreted halo population; (2) the canonical thick disk and halo are not chemically distinct in all elements indicating a smooth transition between the thick disk and halo; (3) a subsample of the $\alpha$-poor stars at metallicities as low as [Fe/H] $\sim$ -0.85 dex are chemically and dynamically consistent with the thin disk indicating that the thin disk may extend to lower metallicities than previously thought, and (4) that the location of the most metal-poor thin disk stars are consistent with a negative radial metallicity gradient. Finally, we used our analysis to suggest a new set of chemical abundance planes ([$\alpha$/Fe], [C+N/Fe], [Al/Fe], and [Mg/Mn]) that may be able to chemically label the Galactic components in a clean and efficient way independent of kinematics.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/8547341c3b5aba454d3d0acbc4fdd33ef329722a

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

  1. Joss Bland-Hawthorn
  2. O. Gerhard
  3. I. Minchev
  4. Hans-Walter Rix
  5. P. McMillan
  6. Y. Ting 丁
  7. Kenneth C. Freeman
  8. Martin Asplund

In Instrumentation

  1. Joss Bland-Hawthorn
  2. O. Gerhard
  3. P. McMillan
  4. Kenneth C. Freeman
  5. M. Ness
  6. Geraint F. Lewis
  7. Sanjib Sharma
  8. P. Kafle

Citations in the corpus