A Galactic Self-Portrait: Density Structure and Integrated Properties of the Milky Way Disk
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arXiv
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| Natura: | Preprint |
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2025
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| author | Imig, Julie Holtzman, Jon A. Zasowski, Gail Lian, Jianhui Boardman, Nicholas F. Stone-Martinez, Alexander Mackereth, J. Ted Prescott, Moire K. M. Beaton, Rachael L. Beers, Timothy C. Bizyaev, Dmitry Blanton, Michael R. Cunha, Katia Fernández-Trincado, José G. Fielder, Catherine E. Hasselquist, Sten Hayes, Christian R. Haywood, Misha Jönsson, Henrik Lane, Richard R. Majewski, Steven R. Mészáros, Szabolcs Minchev, Ivan Nidever, David L. Nitschelm, Christian Sobeck, Jennifer |
| author_facet | Imig, Julie Holtzman, Jon A. Zasowski, Gail Lian, Jianhui Boardman, Nicholas F. Stone-Martinez, Alexander Mackereth, J. Ted Prescott, Moire K. M. Beaton, Rachael L. Beers, Timothy C. Bizyaev, Dmitry Blanton, Michael R. Cunha, Katia Fernández-Trincado, José G. Fielder, Catherine E. Hasselquist, Sten Hayes, Christian R. Haywood, Misha Jönsson, Henrik Lane, Richard R. Majewski, Steven R. Mészáros, Szabolcs Minchev, Ivan Nidever, David L. Nitschelm, Christian Sobeck, Jennifer |
| contents | The evolution 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 ($R \leq 20$ kpc) into sub-populations of metallicity ($Δ$[M/H]$= 0.1$ dex), age ($Δ\log(\frac{\textrm{age}}{\textrm{yr}})= 0.1$), and $α$-element abundances ([$α$/M]). We fit the present-day structural parameters and density distribution of each stellar sub-population 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 $5.27^{+0.2}_{-1.5} \times 10^{10}$ M$_\odot$ and the average mass-weighted scale length is $R_{d} = 2.37 \pm 0.2$ kpc. The Milky Way's present-day color of $(g-r) = 0.72 \pm 0.02$ 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 $\sim 3$ Gyr. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2507_17629 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | A Galactic Self-Portrait: Density Structure and Integrated Properties of the Milky Way Disk Imig, Julie Holtzman, Jon A. Zasowski, Gail Lian, Jianhui Boardman, Nicholas F. Stone-Martinez, Alexander Mackereth, J. Ted Prescott, Moire K. M. Beaton, Rachael L. Beers, Timothy C. Bizyaev, Dmitry Blanton, Michael R. Cunha, Katia Fernández-Trincado, José G. Fielder, Catherine E. Hasselquist, Sten Hayes, Christian R. Haywood, Misha Jönsson, Henrik Lane, Richard R. Majewski, Steven R. Mészáros, Szabolcs Minchev, Ivan Nidever, David L. Nitschelm, Christian Sobeck, Jennifer Astrophysics of Galaxies The evolution 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 ($R \leq 20$ kpc) into sub-populations of metallicity ($Δ$[M/H]$= 0.1$ dex), age ($Δ\log(\frac{\textrm{age}}{\textrm{yr}})= 0.1$), and $α$-element abundances ([$α$/M]). We fit the present-day structural parameters and density distribution of each stellar sub-population 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 $5.27^{+0.2}_{-1.5} \times 10^{10}$ M$_\odot$ and the average mass-weighted scale length is $R_{d} = 2.37 \pm 0.2$ kpc. The Milky Way's present-day color of $(g-r) = 0.72 \pm 0.02$ 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 $\sim 3$ Gyr. |
| title | A Galactic Self-Portrait: Density Structure and Integrated Properties of the Milky Way Disk |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2507.17629 |