The Milky Way tomography with APOGEE: intrinsic density distribution and structure of mono-abundance populations

Author:

Lian Jianhui12ORCID,Zasowski Gail2,Mackereth Ted3ORCID,Imig Julie4,Holtzman Jon A4,Beaton Rachael L56,Bird Jonathan C7ORCID,Cunha Katia89,Fernández-Trincado José G10ORCID,Horta Danny11ORCID,Lane Richard R12,Masters Karen L13ORCID,Nitschelm Christian14,Roman-Lopes A15

Affiliation:

1. Max Planck Institute for Astronomy , D-69117 Heidelberg, Germany

2. Department of Physics and Astronomy, University of Utah , Salt Lake City, UT 84112, USA

3. Dunlap Institute for Astronomy and Astrophysics, University of Toronto , Toronto, ON M5S 3H4, Canada

4. Department of Astronomy, New Mexico State University , Las Cruces, NM 88003, USA

5. The Observatories of the Carnegie Institution for Science , 813 Santa Barbara Street, Pasadena, CA 91101, USA

6. Department of Astrophysical Sciences, Princeton University , 4 Ivy Lane, Princeton, NJ 08544, USA

7. Department of Physics and Astronomy, Vanderbilt University , 6301 Stevenson Center, Nashville, TN 37235, USA

8. Steward Observatory, The University of Arizona , Tucson, AZ 85719, USA

9. Observatório Nacional, 20921-400 So Cristóvao , Rio de Janeiro, RJ 20921-400, Brazil

10. Instituto de Astronomía, Universidad Católica del Norte , Av. Angamos 0610, Antofagasta, Chile

11. Astrophysics Research Institute, Brownlow Hill , Liverpool L3 5RF, UK

12. Instituto de Astrofisica, Pontificia Universidad Católica de Chile , Av. Vicuna Mackenna 4860, 782-0436 Macul, Santiago, Chile

13. Departments of Physics and Astronomy, Haverford College , 370 Lancaster Avenue, Haverford, PA 19041, USA

14. Centro de Astronomía (CITEVA), Universidad de Antofagasta , Avenida Angamos 601, Antofagasta 1270300, Chile

15. Departamento de Astronomía, Universidad La Serena , La Serena, Chile

Abstract

ABSTRACT The spatial distribution of mono-abundance populations (MAPs, selected in [Fe/H] and [Mg/Fe]) reflect the chemical and structural evolution in a galaxy and impose strong constraints on galaxy formation models. In this paper, we use APOGEE data to derive the intrinsic density distribution of MAPs in the Milky Way, after carefully considering the survey selection function. We find that a single exponential profile is not a sufficient description of the Milky Way’s disc. Both the individual MAPs and the integrated disc exhibit a broken radial density distribution; densities are relatively constant with radius in the inner Galaxy and rapidly decrease beyond the break radius. We fit the intrinsic density distribution as a function of radius and vertical height with a 2D density model that considers both a broken radial profile and radial variation of scale height (i.e. flaring). There is a large variety of structural parameters between different MAPs, indicative of strong structure evolution of the Milky Way. One surprising result is that high-α MAPs show the strongest flaring. The young, solar-abundance MAPs present the shortest scale height and least flaring, suggesting recent and ongoing star formation confined to the disc plane. Finally we derive the intrinsic density distribution and corresponding structural parameters of the chemically defined thin and thick discs. The chemical thick and thin discs have local surface mass densities of 5.62 ± 0.08 and 15.69 ± 0.32 M⊙pc−2, respectively, suggesting a massive thick disc with a local surface mass density ratio between thick to thin disc of 36 per cent.

Funder

National Science Foundation

Carnegie Mellon University

Harvard-Smithsonian Center for Astrophysics

University of Tokyo

Lawrence Berkeley National Laboratory

New Mexico State University

New York University

University of Notre Dame

Pennsylvania State University

Universidad Nacional Autónoma de México

University of Arizona

University of Colorado Boulder

University of Portsmouth

University of Utah

University of Virginia

University of Washington

Vanderbilt University

Yale University

Publisher

Oxford University Press (OUP)

Subject

Space and Planetary Science,Astronomy and Astrophysics

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