A Galactic Self-portrait: Density Structure and Integrated Properties of the Milky Way Disk

Abstract The evolutionary history of the Milky Way disk is imprinted in the ages, positions, and chemical compositions of individual stars. In this study, we derive the intrinsic density distribution of different stellar populations using the final data release of the Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey. A total of 203,197 red giant branch stars are used to sort the stellar disk ( R ≤ 20 kpc) into subpopulations of metallicity (Δ[M/H] = 0.1 dex), age ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi mathvariant="normal">Δ</mml:mi> <mml:mi>log</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:mfrac> <mml:mrow> <mml:mi mathvariant="normal">age</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">yr</mml:mi> </mml:mrow> </mml:mfrac> <mml:mo stretchy="false">)</mml:mo> <mml:mspace width="0.25em"/> <mml:mo>=</mml:mo> <mml:mspace width="0.25em"/> <mml:mn>0.1</mml:mn> </mml:math> ), and α -element abundances ([ α /M]). We fit the present-day structural parameters and density distribution of each stellar subpopulation after correcting for the survey selection function. The low- α disk is characterized by longer scale lengths and shorter scale heights, and is best fit by a broken exponential radial profile for each population. The high- α disk is characterized by shorter scale lengths and larger scale heights, and is generally well-approximated by a single exponential radial profile. These results are applied to produce new estimates of the integrated properties of the Milky Way from early times to the present day. We measure the total stellar mass of the disk to be <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>5.2</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>7</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1.5</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.2</mml:mn> </mml:mrow> </mml:msubsup> <mml:mo>×</mml:mo> <mml:mn>1</mml:mn> <mml:msup> <mml:mrow> <mml:mn>0</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> </mml:msup> </mml:math> M ⊙ , and the average mass-weighted scale length is R d = 2.37 ± 0.2 kpc. The Milky Way’s present-day color of ( g − r ) = 0.72 ± 0.02 is consistent with the classification of a red spiral galaxy, although it has only been in the “green valley” region of the galaxy color–mass diagram for the last ∼3 Gyr.

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Journal
The Astrophysical Journal
Published
2025-09-10
DOI
https://doi.org/10.3847/1538-4357/adf723
Citations
3
Primary Topic
Stellar, planetary, and galactic studies
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article
Field-Weighted Citation Impact
3.46
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article

A Galactic Self-portrait: Density Structure and Integrated Properties of the Milky Way Disk

Timothy C. Beers, Jon A. Holtzman, Szabolcs Mészáros, David L. Nidever et al.
3 citations
The Astrophysical Journal
Stellar, planetary, and galactic studies
3.46
article

A Galactic Self-portrait: Density Structure and Integrated Properties of the Milky Way Disk

Timothy C. Beers, Jon A. Holtzman, Szabolcs Mészáros, David L. Nidever, José G. Fernández-Trincado, Richard R. Lane, Julie Imig, M. Haywood, Alexander Stone-Martinez, Jennifer Sobeck, Christian Nıtschelm, Moire K. M. Prescott, Dmitry Bizyaev, Ivan Minchev, Rachael L. Beaton, Sten Hasselquist, Henrik Jönsson, Kátia Cunha, Gail Zasowski, J. Ted Mackereth, Christian R. Hayes, Nicholas Fraser Boardman, Michael R. Blanton, Jianhui Lian, Catherine E. Fielder, Steven R. Majewski
article en
3 citations

Abstract

Abstract The evolutionary history of the Milky Way disk is imprinted in the ages, positions, and chemical compositions of individual stars. In this study, we derive the intrinsic density distribution of different stellar populations using the final data release of the Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey. A total of 203,197 red giant branch stars are used to sort the stellar disk ( R ≤ 20 kpc) into subpopulations of metallicity (Δ[M/H] = 0.1 dex), age ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi mathvariant="normal">Δ</mml:mi> <mml:mi>log</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:mfrac> <mml:mrow> <mml:mi mathvariant="normal">age</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">yr</mml:mi> </mml:mrow> </mml:mfrac> <mml:mo stretchy="false">)</mml:mo> <mml:mspace width="0.25em"/> <mml:mo>=</mml:mo> <mml:mspace width="0.25em"/> <mml:mn>0.1</mml:mn> </mml:math> ), and α -element abundances ([ α /M]). We fit the present-day structural parameters and density distribution of each stellar subpopulation after correcting for the survey selection function. The low- α disk is characterized by longer scale lengths and shorter scale heights, and is best fit by a broken exponential radial profile for each population. The high- α disk is characterized by shorter scale lengths and larger scale heights, and is generally well-approximated by a single exponential radial profile. These results are applied to produce new estimates of the integrated properties of the Milky Way from early times to the present day. We measure the total stellar mass of the disk to be <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>5.2</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>7</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1.5</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.2</mml:mn> </mml:mrow> </mml:msubsup> <mml:mo>×</mml:mo> <mml:mn>1</mml:mn> <mml:msup> <mml:mrow> <mml:mn>0</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> </mml:msup> </mml:math> M ⊙ , and the average mass-weighted scale length is R d = 2.37 ± 0.2 kpc. The Milky Way’s present-day color of ( g − r ) = 0.72 ± 0.02 is consistent with the classification of a red spiral galaxy, although it has only been in the “green valley” region of the galaxy color–mass diagram for the last ∼3 Gyr.

The Astrophysical JournalVol. 990(2)
New Mexico State University (US), Eötvös Loránd University (HU), University of Notre Dame (US), Centre National de la Recherche Scientifique (FR), Space Telescope Science Institute (US), Universidad de Antofagasta (CL), University of Arizona (US), University of St Andrews (GB), University of Pittsburgh (US), Malmö University (SE), University of Toronto (CA), Yunnan University (CN), Joint Institute for Nuclear Astrophysics (US), Carnegie Institution for Science (US), Lomonosov Moscow State University (RU), Princeton University (US), University of Washington (US), Université Paris Cité (FR), University of Utah (US), Montana State University (US), Université Paris Sciences et Lettres (FR), Leibniz Institute for Astrophysics Potsdam (DE), Universidad Católica del Norte (CL), Universidad Bernardo O'Higgins (CL), Sorbonne Paris Cité (FR), Galaxies, Etoiles, Physique et Instrumentation (FR), Université Bourgogne Franche-Comté (FR), Carnegie Observatories (US), MTA-SZTE Research Group on Artificial Intelligence (HU), University of Virginia (US), New York University (US)
Openalex Percentile: Top 7%
Stellar, planetary, and galactic studies
3.46
DOIOpen Access PDFOpenAlex
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