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Linking dwarf galaxies to halo building blocks with the most metal-poor star in Sculptor

Nature volume 464, pages 72–75 (2010)Cite this article

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Abstract

Current cosmological models1,2 indicate that the Milky Way’s stellar halo was assembled from many smaller systems. On the basis of the apparent absence of the most metal-poor stars in present-day dwarf galaxies, recent studies3 claimed that the true Galactic building blocks must have been vastly different from the surviving dwarfs. The discovery of an extremely iron-poor star (S1020549) in the Sculptor dwarf galaxy based on a medium-resolution spectrum4 cast some doubt on this conclusion. Verification of the iron-deficiency, however, and measurements of additional elements, such as the α-element Mg, are necessary to demonstrate that the same type of stars produced the metals found in dwarf galaxies and the Galactic halo. Only then can dwarf galaxy stars be conclusively linked to early stellar halo assembly. Here we report high-resolution spectroscopic abundances for 11 elements in S1020549, confirming its iron abundance of less than 1/4,000th that of the Sun, and showing that the overall abundance pattern follows that seen in low-metallicity halo stars, including the α-elements. Such chemical similarity indicates that the systems destroyed to form the halo billions of years ago were not fundamentally different from the progenitors of present-day dwarfs, and suggests that the early chemical enrichment of all galaxies may be nearly identical.

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Figure 1: Spectral comparison of S1020549 with two other metal-poor stars.
Figure 2: Abundance ratios as a function of iron abundance in S1020549 and other metal-poor stars.

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References

  1. Moore, B. et al. Dark matter substructure within galactic halos. Astrophys. J. 524, L19–L22 (1999)

    Article  ADS  CAS  Google Scholar 

  2. Bullock, J. S. & Johnston, K. V. Tracing galaxy formation with stellar halos. I. Methods. Astrophys. J. 634, 931–949 (2005)

    Article  ADS  Google Scholar 

  3. Helmi, A. et al. A new view of the dwarf spheroidal satellites of the Milky Way from VLT FLAMES: where are the very metal-poor stars? Astrophys. J. 651, L121–L124 (2006)

    Article  ADS  CAS  Google Scholar 

  4. Kirby, E. N., Guhathakurta, P., Bolte, M., Sneden, C. & Geha, M. C. Multi-element abundance measurements from medium-resolution spectra. I. The Sculptor dwarf spheroidal galaxy. Astrophys. J. 705, 328–346 (2009)

    Article  ADS  CAS  Google Scholar 

  5. Shetrone, M. et al. VLT/UVES abundances in four nearby dwarf spheroidal galaxies. I. Nucleosynthesis and abundance ratios. Astron. J. 125, 684–706 (2003)

    Article  ADS  CAS  Google Scholar 

  6. Geisler, D., Smith, V. V., Wallerstein, G., Gonzalez, G. & Charbonnel, C. “Sculptor-ing” the galaxy? The chemical compositions of red giants in the Sculptor dwarf spheroidal galaxy. Astron. J. 129, 1428–1442 (2005)

    Article  ADS  CAS  Google Scholar 

  7. Venn, K. A. et al. Stellar chemical signatures and hierarchical galaxy formation. Astron. J. 128, 1177–1195 (2004)

    Article  ADS  CAS  Google Scholar 

  8. Searle, L. & Zinn, R. Compositions of halo clusters and the formation of the galactic halo. Astrophys. J. 225, 357–379 (1978)

    Article  ADS  CAS  Google Scholar 

  9. Kirby, E. N., Guhathakurta, P. & Sneden, C. Metallicity and alpha-element abundance measurement in red giant stars from medium-resolution spectra. Astrophys. J. 682, 1217–1233 (2008)

    Article  ADS  CAS  Google Scholar 

  10. Bernstein, R., Shectman, S. A., Gunnels, S. M., Mochnacki, S. & Athey, A. E. MIKE: a double echelle spectrograph for the Magellan telescopes at Las Campanas Observatory. Soc. SPIE Conf. Ser. (eds Iye, M. & Moorwood, A. F. M.) 4841, 1694–1704 (2003)

    ADS  Google Scholar 

  11. Battaglia, G. et al. The kinematic status and mass content of the Sculptor dwarf spheroidal galaxy. Astrophys. J. 681, L13–L16 (2008)

    Article  ADS  CAS  Google Scholar 

  12. Frebel, A., Simon, J. D., Geha, M. & Willman, B. High-resolution spectroscopy of extremely metal-poor stars in the least evolved galaxies: Ursa Major II and Coma Berenices. Astrophys. J. 708, 560–583 (2010)

    Article  ADS  CAS  Google Scholar 

  13. Cayrel, R. et al. First stars V—Abundance patterns from C to Zn and supernova yields in the early Galaxy. Astron. Astrophys. 416, 1117–1138 (2004)

    Article  ADS  CAS  Google Scholar 

  14. Fulbright, J. P., Rich, R. M. & Castro, S. Draco 119: a remarkable heavy-element-deficient giant. Astrophys. J. 612, 447–453 (2004)

    Article  ADS  CAS  Google Scholar 

  15. Koch, A., McWilliam, A., Grebel, E. K., Zucker, D. B. & Belokurov, V. The highly unusual chemical composition of the Hercules dwarf spheroidal galaxy. Astrophys. J. 688, L13–L16 (2008)

    Article  ADS  CAS  Google Scholar 

  16. Schoerck, T. et al. The stellar content of the Hamburg/ESO survey. V. The metallicity distribution function of the Galactic halo. Astron. Astrophys. 507, 817–832 (2009)

    Article  ADS  Google Scholar 

  17. Frebel, A. et al. Nucleosynthetic signatures of the first stars. Nature 434, 871–873 (2005)

    Article  ADS  CAS  Google Scholar 

  18. Kirby, E. N., Simon, J. D., Geha, M., Guhathakurta, P. & Frebel, A. Uncovering extremely metal-poor stars in the Milky Way’s ultra-faint dwarf spheroidal satellite galaxies. Astrophys. J. 685, L43–L46 (2008)

    Article  ADS  CAS  Google Scholar 

  19. Pietrzynski, G. et al. The Araucaria project: the distance to the Sculptor dwarf spheroidal galaxy from infrared photometry of RR Lyrae stars. Astron. J. 135, 1993–1997 (2008)

    Article  ADS  Google Scholar 

  20. Carollo, D. et al. Two stellar components in the halo of the Milky Way. Nature 450, 1020–1025 (2007)

    Article  ADS  CAS  Google Scholar 

  21. Simon, J. D. & Geha, M. The kinematics of the ultra-faint Milky Way satellites: solving the missing satellite problem. Astrophys. J. 670, 313–331 (2007)

    Article  ADS  CAS  Google Scholar 

  22. Robertson, B., Bullock, J. S., Font, A. S., Johnston, K. V. & Hernquist, L. Lambda cold dark matter, stellar feedback, and the galactic halo abundance pattern. Astrophys. J. 632, 872–881 (2005)

    Article  ADS  CAS  Google Scholar 

  23. Font, A. S., Johnston, K. V., Bullock, J. S. & Robertson, B. E. Phase-space distributions of chemical abundances in Milky Way-type galaxy halos. Astrophys. J. 646, 886–898 (2006)

    Article  ADS  CAS  Google Scholar 

  24. Asplund, M., Grevesse, N., Sauval, A. J. & Scott, P. The chemical composition of the Sun. Annu. Rev. Astron. Astrophys. 47, 481–522 (2009)

    Article  ADS  CAS  Google Scholar 

  25. Geha, M. et al. The least-luminous galaxy: spectroscopy of the Milky Way satellite segue 1. Astrophys. J. 692, 1464–1475 (2009)

    Article  ADS  CAS  Google Scholar 

  26. Barklem, P. S. et al. The Hamburg/ESO R-process enhanced star survey (HERES). II. Spectroscopic analysis of the survey sample. Astron. Astrophys. 439, 129–151 (2005)

    Article  ADS  CAS  Google Scholar 

  27. Frebel, A. et al. Chemical abundance analysis of the extremely metal-poor star HE 1300+0157. Astrophys. J. 658, 534–552 (2007)

    Article  ADS  CAS  Google Scholar 

  28. Lai, D. K. et al. Detailed abundances for 28 metal-poor stars: stellar relics in the Milky Way. Astrophys. J. 681, 1524–1556 (2008)

    Article  ADS  CAS  Google Scholar 

  29. Aoki, W. et al. Chemical composition of extremely metal-poor stars in the Sextans dwarf spheroidal galaxy. Astron. Astrophys. 502, 569–578 (2009)

    Article  ADS  CAS  Google Scholar 

  30. Cohen, J. G. & Huang, W. The chemical evolution of the Draco dwarf spheroidal galaxy. Astrophys. J. 701, 1053–1075 (2009)

    Article  ADS  CAS  Google Scholar 

Download references

Acknowledgements

Our data was gathered using the 6.5-m Magellan telescopes located at Las Campanas Observatory, Chile. We thank L. Hernquist for discussions on galaxy formation. A.F. acknowledges support through a Clay Fellowship administered by the Smithsonian Astrophysical Observatory. Support for this work was provided by NASA through a Hubble fellowship grant awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA (to E.N.K., who is a Hubble Fellow). J.D.S. acknowledges the support of a Vera Rubin Fellowship provided by the Carnegie Institution of Washington.

Author Contributions A.F. took the high-resolution observations, and led the analysis; E.N.K. provided the target; J.D.S. contributed to the analysis. All authors contributed to the writing of the paper.

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Authors and Affiliations

  1. Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts 02138, USA ,

    Anna Frebel

  2. California Institute of Technology, Pasadena, California 91106, USA ,

    Evan N. Kirby

  3. Observatories of the Carnegie Institution of Washington, Pasadena, California 91101, USA ,

    Joshua D. Simon

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  1. Anna Frebel
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  2. Evan N. Kirby
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Correspondence to Anna Frebel.

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Frebel, A., Kirby, E. & Simon, J. Linking dwarf galaxies to halo building blocks with the most metal-poor star in Sculptor. Nature 464, 72–75 (2010). https://doi.org/10.1038/nature08772

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