The Stellar Velocity Distribution Function in the Milky Way Galaxy

Journal Article · Wed Jul 01 04:00:00 EDT 2020 · The Astronomical Journal (Online)

DOI:https://doi.org/10.3847/1538-3881/AB9813· OSTI ID:23013275

Anguiano, Borja; Majewski, Steven R.; Hayes, Christian R.; Cheng, Xinlun ^[1]; Prieto, Carlos Allende ^[2]; Bidin, Christian Moni ^[3]; Beaton, Rachael L. ^[4]; Beers, Timothy C. ^[5]; Minniti, Dante ^[6]

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1. Department of Astronomy, University of Virginia, Charlottesville, VA, 22904 (United States)
2. Instituto de Astrofísica de Canarias (IAC), E-38205 La Laguna, Tenerife (Spain)
3. Instituto de Astronomía, Universidad Católica del Norte, Av. Angamos 0610, Antofagasta (Chile)
4. Department of Astrophysical Sciences, Princeton University, 4 Ivy Lane, Princeton, NJ 08544 (United States)
5. Department of Physics and JINA Center for the Evolution of the Elements, University of Notre Dame, Notre Dame, IN 46556 (United States)
6. Depto. de Cs. Físicas, Facultad de Ciencias Exactas, Universidad Andrés Bello, Av. Fernández Concha 700, Las Condes, Santiago (Chile)

The stellar velocity distribution function in the solar vicinity is reexamined using data from the Sloan Digital Sky Survey Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey’s DR16 and Gaia DR2. By exploiting APOGEE’s ability to chemically discriminate with great reliability the thin-disk, thick-disk, and (accreted) halo populations, we can, for the first time, derive the three-dimensional velocity distribution functions (DFs) for these chemically separated populations. We employ this smaller but more data-rich APOGEE+Gaia sample to build a data-driven model of the local stellar population velocity DFs and use these as basis vectors for assessing the relative density proportions of these populations over the 5 < R < 12 kpc and −1.5 < z < 2.5 kpc range as derived from the larger, more complete (i.e., all-sky, magnitude-limited) Gaia database. We find that 81.9% ± 3.1% of the objects in the selected Gaia data set are thin-disk stars, 16.6% ± 3.2% are thick-disk stars, and 1.5% ± 0.1% belong to the Milky Way stellar halo. We also find the local thick-to-thin-disk density normalization to be ρ {sub T}(R {sub ⊙})/ρ {sub t}(R {sub ⊙}) = 2.1% ± 0.2%, a result consistent with, but determined in a completely different way from, typical star-count/density analyses. Using the same methodology, the local halo-to-disk-density normalization is found to be ρ {sub H}(R {sub ⊙})/(ρ {sub T}(R {sub ⊙}) + ρ {sub t}(R {sub ⊙})) = 1.2% ± 0.6%, a value that may be inflated due to the chemical overlap of halo and metal-weak thick-disk stars.

• OSTI ID: 23013275
• Journal Information: The Astronomical Journal (Online), Journal Name: The Astronomical Journal (Online) Journal Issue: 1 Vol. 160; ISSN 1538-3881
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
DISTRIBUTION FUNCTIONS
GALACTIC EVOLUTION
METALS
MILKY WAY
RELIABILITY
STARS
THREE-DIMENSIONAL CALCULATIONS
VELOCITY