Gravitational collapse and the thermal evolution of low-metallicity gas clouds in the early Universe

被引:43
作者
Chiaki, Gen [1 ,2 ]
Yoshida, Naoki [1 ,3 ]
Hirano, Shingo [1 ,4 ]
机构
[1] Univ Tokyo, Grad Sch Sci, Dept Phys, Bunkyo Ku, 7-3-1 Hongo, Tokyo 1130033, Japan
[2] Konan Univ, Dept Phys, 8-9-1 Okamoto, Kobe, Hyogo 6580072, Japan
[3] Univ Tokyo, Todai Inst Adv Study, Kavli Inst Phys & Math Universe WPI, Kashiwa, Chiba 2778583, Japan
[4] Univ Texas Austin, Dept Astron, RLM 15308, Austin, TX 78712 USA
基金
日本学术振兴会;
关键词
stars: formation; stars: low-mass; stars: Population II; ISM: abundances; dust; extinction; galaxies: evolution; STAR-FORMING CLOUDS; POPULATION III STARS; LOW-MASS STARS; ROTATING ISOTHERMAL CLOUDS; METAL-POOR STARS; 1ST STARS; INITIAL CONDITIONS; MOLECULAR CLOUDS; DUST GRAINS; CHEMICAL EVOLUTION;
D O I
10.1093/mnras/stw2120
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We study gravitational collapse of low-metallicity gas clouds and the formation of protostars by three-dimensional hydrodynamic simulations. Grain growth, non-equilibrium chemistry, molecular cooling, and chemical heating are solved in a self-consistent manner for the first time. We employ the realistic initial conditions for the abundances of metal and dust, and the dust size distribution obtained from recent Population III supernova calculations. We also introduce the state-of-the-art particle splitting method based on the Voronoi tessellation and achieve an extremely high mass resolution of similar to 10(-5) M-circle dot (10 Earth masses) in the central region. We follow the thermal evolution of several clouds with various metallicities. We show that the condition for cloud fragmentation depends not only on the gas metallicity but also on the collapse time-scale. In many cases, the cloud fragmentation is prevented by the chemical heating owing to molecular hydrogen formation even though dust cooling becomes effective. Meanwhile, in several cases, efficient OH and H2O cooling promotes the cloud elongation, and then cloud 'filamentation' is driven by dust thermal emission as a precursor of eventual fragmentation. While the filament fragmentation is driven by rapid gas cooling with metallicity greater than or similar to 10(-5) Z(circle dot), fragmentation occurs in a different manner by the self-gravity of a circumstellar disc with metallicity less than or similar to 10(-5) Z(circle dot). We use a semi-analytic model to estimate the number fraction of the clouds which undergo the filament fragmentation to be 20-40 per cent with metallicity 10(-5)-10(-4) Z(circle dot). Overall, our simulations show a viable formation path of the recently discovered Galactic low-mass stars with extremely small metallicities.
引用
收藏
页码:2781 / 2798
页数:18
相关论文
共 90 条
  • [1] THE CHEMICAL IMPRINT OF SILICATE DUST ON THE MOST METAL-POOR STARS
    Alexander, P., Jr.
    Frebel, Anna
    Bromm, Volker
    [J]. ASTROPHYSICAL JOURNAL, 2014, 782 (02)
  • [2] [Anonymous], 1980, The large-scale structure of the universe, DOI DOI 10.23943/PRINCETON/9780691209838.001.0001
  • [3] A chemical signature of first-generation very massive stars
    Aoki, W.
    Tominaga, N.
    Beers, T. C.
    Honda, S.
    Lee, Y. S.
    [J]. SCIENCE, 2014, 345 (6199) : 912 - 915
  • [4] AUDOUZE J, 1995, ASTROPHYS J, V451, pL49, DOI 10.1086/309687
  • [5] Bovino S., 2016, ARXIV160104525
  • [6] The formation of the first low-mass stars from gas with low carbon and oxygen abundances
    Bromm, V
    Loeb, A
    [J]. NATURE, 2003, 425 (6960) : 812 - 814
  • [7] A universal angular momentum profile for galactic halos
    Bullock, JS
    Dekel, A
    Kolatt, TS
    Kravtsov, AV
    Klypin, AA
    Porciani, C
    Primack, JR
    [J]. ASTROPHYSICAL JOURNAL, 2001, 555 (01) : 240 - 257
  • [8] A primordial star in the heart of the Lion
    Caffau, E.
    Bonifacio, P.
    Francois, P.
    Spite, M.
    Spite, F.
    Zaggia, S.
    Ludwig, H. -G.
    Steffen, M.
    Mashonkina, L.
    Monaco, L.
    Sbordone, L.
    Molaro, P.
    Cayrel, R.
    Plez, B.
    Hill, V.
    Hammer, F.
    Randich, S.
    [J]. ASTRONOMY & ASTROPHYSICS, 2012, 542
  • [9] Solar Chemical Abundances Determined with a CO5BOLD 3D Model Atmosphere
    Caffau, E.
    Ludwig, H. -G.
    Steffen, M.
    Freytag, B.
    Bonifacio, P.
    [J]. SOLAR PHYSICS, 2011, 268 (02) : 255 - 269
  • [10] An extremely primitive star in the Galactic halo
    Caffau, Elisabetta
    Bonifacio, Piercarlo
    Francois, Patrick
    Sbordone, Luca
    Monaco, Lorenzo
    Spite, Monique
    Spite, Francois
    Ludwig, Hans-G.
    Cayrel, Roger
    Zaggia, Simone
    Hammer, Francois
    Randich, Sofia
    Molaro, Paolo
    Hill, Vanessa
    [J]. NATURE, 2011, 477 (7362) : 67 - 69