New Families in our Solar Neighborhood: Applying Gaussian Mixture Models for Objective Classification of Structures in the Milky Way and in Simulations

被引：6

作者：

Nikakhtar, Farnik ^{[1
]}

Sanderson, Robyn E. ^{[1
,2
]}

Wetzel, Andrew ^{[3
]}

Loebman, Sarah ^{[3
,4
]}

Sharma, Sanjib ^{[5
,6
]}

Beaton, Rachael ^{[7
,8
]}

Mackereth, J. Ted ^{[9
,10
]}

Poovelil, Vijith Jacob ^{[11
]}

Zasowski, Gail ^{[11
]}

Bonaca, Ana ^{[12
]}

Martell, Sarah ^{[6
,13
]}

Jonsson, Henrik ^{[14
]}

Faucher-Giguere, Claude-Andre ^{[15
,16
]}

机构：

[1] Univ Penn, Dept Phys & Astron, 209 S 33rd St, Philadelphia, PA 19104 USA

[2] Flatiron Inst, Ctr Computat Astrophys, 162 5th Ave, New York, NY 10010 USA

[3] Univ Calif Davis, Dept Phys & Astron, Davis, CA 95616 USA

[4] Univ Calif Merced, Dept Phys, 5200 North Lake Rd, Merced, CA 95343 USA

[5] Univ Sydney, Sch Phys, Sydney Inst Astron, A28, Sydney, NSW 2006, Australia

[6] Ctr Excellence Astrophys Three Dimens ASTRO 3D, Canberra, ACT, Australia

[7] Princeton Univ, Dept Astrophys Sci, 4 Ivy Lane, Princeton, NJ 08544 USA

[8] Observ Carnegie Inst Sci, 813 Santa Barbara St, Pasadena, CA 91101 USA

[9] Univ Toronto, Canadian Inst Theoret Astrophys, 60 St George St, Toronto, ON M5S 3H8, Canada

[10] Univ Toronto, Dunlap Inst Astron & Astrophys, 50 St George St, Toronto, ON M5S 3H4, Canada

[11] Univ Utah, Dept Phys & Astron, Salt Lake City, UT 84112 USA

[12] Ctr Astrophys Harvard & Smithsonian, 60 Garden St, Cambridge, MA 02138 USA

[13] UNSW, Sch Phys, Sydney, NSW 2052, Australia

[14] Malmo Univ, Mat Sci & Appl Math, SE-20506 Malmo, Sweden

[15] Northwestern Univ, Dept Phys & Astron, 2145 Sheridan Rd, Evanston, IL 60208 USA

[16] Northwestern Univ, CIERA, 2145 Sheridan Rd, Evanston, IL 60208 USA

来源：

ASTROPHYSICAL JOURNAL | 2021年 / 921卷 / 02期

基金：

澳大利亚研究理事会; 美国国家科学基金会;

关键词：

LOW-METALLICITY STARS; INNER STELLAR HALO; METAL-POOR STARS; FIRE SIMULATIONS; CO-FORMATION; DATA RELEASE; THICK DISKS; LOCAL GROUP; F-DWARF; GALAXY;

D O I：

10.3847/1538-4357/ac1a10

中图分类号：

P1 [天文学];

学科分类号：

0704 ;

摘要：

The standard picture of galaxy formation motivates the decomposition of the Milky Way into 3-4 stellar populations with distinct kinematic and elemental abundance distributions: the thin disk, thick disk, bulge, and stellar halo. To test this idea, we construct a Gaussian mixture model (GMM) for both simulated and observed stars in the solar neighborhood, using measured velocities and iron abundances (i.e., an augmented Toomre diagram) as the distributions to be decomposed. We compare results for the Gaia-APOGEE DR16 crossmatch catalog of the solar neighborhood with those from a suite of synthetic Gaia-APOGEE crossmatches constructed from FIRE-2 cosmological simulations of Milky Way mass galaxies. We find that in both the synthetic and real data, the best-fit GMM uses five independent components, some of whose properties resemble the standard populations predicted by galaxy formation theory. Two components can be identified unambiguously as the thin disk and another as the halo. However, instead of a single counterpart to the thick disk, there are three intermediate components with different age and alpha abundance distributions (although these data are not used to construct the model). We use decompositions of the synthetic data to show that the classified components indeed correspond to stars with different origins. By analogy with the simulated data, we show that our mixture model of the real Gaia-APOGEE crossmatch distinguishes the following components: (1) a classic thin disk of young stars on circular orbits (46%), (2) thin disk stars heated by interactions with satellites (22%), (3, 4) two components representing the velocity asymmetry of the alpha-enhanced thick disk (27%), and (5) a stellar halo consistent with early, massive accretion (4%).

引用

页数：17