A galactic self-portrait: density structure and integrated properties of the Milky Way disk

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

doi:10.3847/1538-4357/adf723

A galactic self-portrait: density structure and integrated properties of the Milky Way disk

Julie Imig^*, Jon A. Holtzman, Gail Zasowski, Jianhui Lian, Nicholas F. Boardman, Alexander Stone-Martinez, J. Ted Mackereth, Moire K. M. Prescott, Rachael L. Beaton, Timothy C. Beers, Dmitry Bizyaev, Michael R. Blanton, Katia Cunha, José G. Fernández-Trincado, Catherine E. Fielder, Sten Hasselquist, Christian R. Hayes, Misha Haywood, Henrik Jönsson, Richard R. LaneSteven R. Majewski, Szabolcs Mészáros, Ivan Minchev, David L. Nidever, Christian Nitschelm, Jennifer Sobeck

^*Corresponding author for this work

School of Physics and Astronomy

Research output: Contribution to journal › Article › peer-review

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 (Δlog(age/yr) = 0.1), 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 5.27^+0.2_-1.5 × 10¹⁰ 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.

Original language	English
Article number	203
Number of pages	28
Journal	Astrophysical Journal
Volume	990
Issue number	2
DOIs	https://doi.org/10.3847/1538-4357/adf723
Publication status	Published - 10 Sept 2025

Keywords

Milky Way galaxy
Milky Way evolution
Milky Way mass
Galaxy evolution
Stellar populations
Galaxy stellar content

Access to Document

10.3847/1538-4357/adf723Licence: CC BY

Imig_2025_ApJ_Galactic-self-portrait-Milky-Way-disk_CC
© 2025 The Author(s). Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence (https://creativecommons.org/licenses/by/4.0/). Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
Final published version, 15.5 MBLicence: CC BY

Cite this

Imig, J., Holtzman, J. A., Zasowski, G., Lian, J., Boardman, N. F., Stone-Martinez, A., Mackereth, J. T., Prescott, M. K. M., Beaton, R. L., Beers, T. C., Bizyaev, D., Blanton, M. R., Cunha, K., Fernández-Trincado, J. G., Fielder, C. E., Hasselquist, S., Hayes, C. R., Haywood, M., Jönsson, H., ... Sobeck, J. (2025). A galactic self-portrait: density structure and integrated properties of the Milky Way disk. Astrophysical Journal, 990(2), Article 203. https://doi.org/10.3847/1538-4357/adf723

@article{b4e31fa587cf48ffbd66a9d84b560f1f,

title = "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 (Δlog(age/yr) = 0.1), 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 5.27+0.2-1.5 × 1010 M⊙, and the average mass-weighted scale length is Rd = 2.37 ± 0.2 kpc. The Milky Way{\textquoteright}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.",

keywords = "Milky Way galaxy, Milky Way evolution, Milky Way mass, Galaxy evolution, Stellar populations, Galaxy stellar content",

author = "Julie Imig and Holtzman, \{Jon A.\} and Gail Zasowski and Jianhui Lian and Boardman, \{Nicholas F.\} and Alexander Stone-Martinez and Mackereth, \{J. Ted\} and Prescott, \{Moire K. M.\} and Beaton, \{Rachael L.\} and Beers, \{Timothy C.\} and Dmitry Bizyaev and Blanton, \{Michael R.\} and Katia Cunha and Fern{\'a}ndez-Trincado, \{Jos{\'e} G.\} and Fielder, \{Catherine E.\} and Sten Hasselquist and Hayes, \{Christian R.\} and Misha Haywood and Henrik J{\"o}nsson and Lane, \{Richard R.\} and Majewski, \{Steven R.\} and Szabolcs M{\'e}sz{\'a}ros and Ivan Minchev and Nidever, \{David L.\} and Christian Nitschelm and Jennifer Sobeck",

note = "Funding: J.I. gratefully acknowledges support from NSF grant AST-1909897 and STScI DDRF project D0001.82530. J.A.H. also gratefully acknowledges support from NSF grant AST-1909897. N.F.B. acknowledges Science and Technologies Facilities Council (STFC) grant ST/V000861/1. T.C.B acknowledges partial support from grant PHY 14-30152; Physics Frontier Center/JINA Center for the Evolution of the Elements (JINA-CEE), and from OISE-1927130: The International Research Network for Nuclear Astrophysics (IReNA), awarded by the US National Science Foundation. D.B. is partly supported by RSCF grant 22-12-00080. I.M. acknowledges support by the Deutsche Forschungsgemeinschaft under the grant MI 2009/2-1. S.M. has been supported by the LP2021-9 Lend{\"u}let grant of the Hungarian Academy of Sciences, and by the NKFIH excellence grant TKP2021-NKTA-64.",

year = "2025",

month = sep,

day = "10",

doi = "10.3847/1538-4357/adf723",

language = "English",

volume = "990",

journal = "Astrophysical Journal",

issn = "0004-637X",

publisher = "American Astronomical Society",

number = "2",

}

Imig, J, Holtzman, JA, Zasowski, G, Lian, J, Boardman, NF, Stone-Martinez, A, Mackereth, JT, Prescott, MKM, Beaton, RL, Beers, TC, Bizyaev, D, Blanton, MR, Cunha, K, Fernández-Trincado, JG, Fielder, CE, Hasselquist, S, Hayes, CR, Haywood, M, Jönsson, H, Lane, RR, Majewski, SR, Mészáros, S, Minchev, I, Nidever, DL, Nitschelm, C & Sobeck, J 2025, 'A galactic self-portrait: density structure and integrated properties of the Milky Way disk', Astrophysical Journal, vol. 990, no. 2, 203. https://doi.org/10.3847/1538-4357/adf723

TY - JOUR

T1 - A galactic self-portrait

T2 - density structure and integrated properties of the Milky Way disk

AU - Imig, Julie

AU - Holtzman, Jon A.

AU - Zasowski, Gail

AU - Lian, Jianhui

AU - Boardman, Nicholas F.

AU - Stone-Martinez, Alexander

AU - Mackereth, J. Ted

AU - Prescott, Moire K. M.

AU - Beaton, Rachael L.

AU - Beers, Timothy C.

AU - Bizyaev, Dmitry

AU - Blanton, Michael R.

AU - Cunha, Katia

AU - Fernández-Trincado, José G.

AU - Fielder, Catherine E.

AU - Hasselquist, Sten

AU - Hayes, Christian R.

AU - Haywood, Misha

AU - Jönsson, Henrik

AU - Lane, Richard R.

AU - Majewski, Steven R.

AU - Mészáros, Szabolcs

AU - Minchev, Ivan

AU - Nidever, David L.

AU - Nitschelm, Christian

AU - Sobeck, Jennifer

N1 - Funding: J.I. gratefully acknowledges support from NSF grant AST-1909897 and STScI DDRF project D0001.82530. J.A.H. also gratefully acknowledges support from NSF grant AST-1909897. N.F.B. acknowledges Science and Technologies Facilities Council (STFC) grant ST/V000861/1. T.C.B acknowledges partial support from grant PHY 14-30152; Physics Frontier Center/JINA Center for the Evolution of the Elements (JINA-CEE), and from OISE-1927130: The International Research Network for Nuclear Astrophysics (IReNA), awarded by the US National Science Foundation. D.B. is partly supported by RSCF grant 22-12-00080. I.M. acknowledges support by the Deutsche Forschungsgemeinschaft under the grant MI 2009/2-1. S.M. has been supported by the LP2021-9 Lendület grant of the Hungarian Academy of Sciences, and by the NKFIH excellence grant TKP2021-NKTA-64.

PY - 2025/9/10

Y1 - 2025/9/10

N2 - 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 (Δlog(age/yr) = 0.1), 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 5.27+0.2-1.5 × 1010 M⊙, and the average mass-weighted scale length is Rd = 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.

AB - 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 (Δlog(age/yr) = 0.1), 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 5.27+0.2-1.5 × 1010 M⊙, and the average mass-weighted scale length is Rd = 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.

KW - Milky Way galaxy

KW - Milky Way evolution

KW - Milky Way mass

KW - Galaxy evolution

KW - Stellar populations

KW - Galaxy stellar content

U2 - 10.3847/1538-4357/adf723

DO - 10.3847/1538-4357/adf723

M3 - Article

SN - 0004-637X

VL - 990

JO - Astrophysical Journal

JF - Astrophysical Journal

IS - 2

M1 - 203

ER -

A galactic self-portrait: density structure and integrated properties of the Milky Way disk

Abstract

Keywords

Access to Document

Fingerprint

Cite this