Characterizing stellar halo populations - I. An extended distribution function for halo K giants

被引:55
|
作者
Das, Payel [1 ]
Binney, James [1 ]
机构
[1] Univ Oxford, Rudolf Peierls Ctr Theoret Phys, Oxford OX1 3NP, England
基金
英国科学技术设施理事会; 欧洲研究理事会;
关键词
methods: data analysis; Galaxy: halo; Galaxy: kinematics and dynamics; Galaxy: stellar content; MILKY-WAY HALO; BLUE HORIZONTAL-BRANCH; DIGITAL SKY SURVEY; SAGITTARIUS DWARF GALAXY; GALACTIC HALO; METALLICITY DISTRIBUTION; VELOCITY ANISOTROPY; SPHEROIDAL GALAXY; MASS-DISTRIBUTION; DYNAMICAL MODELS;
D O I
10.1093/mnras/stw744
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We fit an extended distribution function (EDF) to K giants in the Sloan Extension for Galactic Understanding and Exploration survey. These stars are detected to radii similar to 80 kpc and span a wide range in [Fe/H]. Our EDF, which depends on [Fe/H] in addition to actions, encodes the entanglement of metallicity with dynamics within the Galaxy's stellar halo. Our maximum-likelihood fit of the EDF to the data allows us to model the survey's selection function. The density profile of the K giants steepens with radius from a slope similar to a'2 to similar to a'4 at large radii. The halo's axis ratio increases with radius from 0.7 to almost unity. The metal-rich stars are more tightly confined in action space than the metal-poor stars and form a more flattened structure. A weak metallicity gradient similar to a'0.001 dex kpc(-1), a small gradient in the dispersion in [Fe/H] of similar to 0.001 dex kpc(-1), and a higher degree of radial anisotropy in metal-richer stars result. Lognormal components with peaks at similar to a'1.5 and similar to a'2.3 are required to capture the overall metallicity distribution, suggestive of the existence of two populations of K giants. The spherical anisotropy parameter varies between 0.3 in the inner halo to isotropic in the outer halo. If the Sagittarius stream is included, a very similar model is found but with a stronger degree of radial anisotropy throughout.
引用
收藏
页码:1725 / 1738
页数:14
相关论文
共 50 条
  • [21] KINEMATICS OF FIELD K-GIANTS IN THE OUTER GALACTIC HALO
    RATNATUNGA, KU
    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC, 1984, 96 (584) : 793 - 794
  • [22] H i HOD. I. The Halo Occupation Distribution of H i Galaxies
    Qin, Fei
    Howlett, Cullan
    Stevens, Adam R. H.
    Parkinson, David
    ASTROPHYSICAL JOURNAL, 2022, 937 (02):
  • [23] The stellar halo in Local Group Hestia simulations I. The in situ component and the effect of mergers
    Khoperskov, Sergey
    Minchev, Ivan
    Libeskind, Noam
    Haywood, Misha
    Di Matteo, Paola
    Belokurov, Vasily
    Steinmetz, Matthias
    Gomez, Facundo A.
    Grand, Robert J. J.
    Hoffman, Yehuda
    Knebe, Alexander
    Sorce, Jenny G.
    Spaare, Martin
    Tempel, Elmo
    Vogelsberger, Mark
    ASTRONOMY & ASTROPHYSICS, 2023, 677
  • [24] Galactic cartography with SkyMapper - I. Population substructure and the stellar number density of the inner halo
    Wan, Zhen
    Kafle, Prajwal R.
    Lewis, Geraint F.
    Mackey, Dougal
    Sharma, Sanjib
    Ibata, Rodrigo A.
    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 2018, 480 (01) : 1218 - 1228
  • [25] On the origin of the stellar halo and multiple stellar populations in the globular cluster NGC 1851
    Bekki, Kenji
    Yong, David
    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 2012, 419 (03) : 2063 - 2076
  • [26] Environmental dependence of dark matter halo growth - I. Halo merger rates
    Fakhouri, Onsi
    Ma, Chung-Pei
    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 2009, 394 (04) : 1825 - 1840
  • [27] On the relative ages of the α-rich and α-poor stellar populations in the Galactic halo
    Hawkins, K.
    Jofre, P.
    Gilmore, G.
    Masseron, T.
    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 2014, 445 (03) : 2575 - 2588
  • [28] Origin of the metallicity distribution of the NGC 5128 stellar halo
    Bekki, K
    Harris, WE
    Harris, GLH
    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 2003, 338 (03) : 587 - 598
  • [29] The stellar populations of halo substructure along the major axis of andromeda
    Richardson, J. C.
    Ferguson, A. M. N.
    Johnson, R. A.
    Faria, D. C.
    FROM STARS TO GALAXIES: BUILDING THE PIECES TO BUILD UP THE UNIVERSE, 2007, 374 : 295 - +
  • [30] A Stochastic Theory of the Hierarchical Clustering. I. Halo Mass Function
    Lapi, Andrea
    Danese, Luigi
    ASTROPHYSICAL JOURNAL, 2020, 903 (02):