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High-resolution Spectroscopy of Extremely Metal-poor Stars in the Least Evolved Galaxies: Leo IV

Simon, Joshua D. and Frebel, Anna and McWilliam, Andrew and Kirby, Evan N. and Thompson, Ian B. (2010) High-resolution Spectroscopy of Extremely Metal-poor Stars in the Least Evolved Galaxies: Leo IV. Astrophysical Journal, 716 (1). pp. 446-452. ISSN 0004-637X.

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We present high-resolution Magellan/MIKE spectroscopy of the brightest star in the ultra-faint dwarf galaxy Leo IV. We measure an iron abundance of [Fe/H] = –3.2, adding to the rapidly growing sample of extremely metal-poor (EMP) stars being identified in Milky Way satellite galaxies. The star is enhanced in the α elements Mg, Ca, and Ti by ~0.3 dex, very similar to the typical Milky Way halo abundance pattern. All of the light and iron-peak elements follow the trends established by EMP halo stars, but the neutron-capture elements Ba and Sr are significantly underabundant. These results are quite similar to those found for stars in the ultra-faint dwarfs Ursa Major II, Coma Berenices, Boötes I, and Hercules, suggesting that the chemical evolution of the lowest-luminosity galaxies may be universal. The abundance pattern we observe is consistent with predictions for nucleosynthesis from a Population III supernova explosion. The extremely low metallicity of this star also supports the idea that a significant fraction (≳10%) of the stars in the faintest dwarfs have metallicities below [Fe/H] = –3.0.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Frebel, Anna0000-0002-2139-7145
Kirby, Evan N.0000-0001-6196-5162
Additional Information:© 2010 American Astronomical Society. Received 2010 January 18; accepted 2010 April 16; published 2010 May 19. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile. We thank Dan Kelson for assistance with the data reduction, Steve Shectman for observing suggestions, Alexander Heger for extensive help with comparisons to theoretical SN models, and the referee for a helpful report. J.D.S gratefully acknowledges the support of a Vera Rubin Fellowship provided by the Carnegie Institution of Washington, and A.F. that of a Clay Fellowship administered by the Smithsonian Astrophysical Observatory. This work was also supported by NASA through Hubble Fellowship grant HST-HF-01233.01 awarded to E.N.K. by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS 5-26555. This research made use of NASA’s Astrophysics Data System Bibliographic Services. Facilities: Magellan:Clay (MIKE)
Funding AgencyGrant Number
Carnegie Mellon Institute of WashingtonUNSPECIFIED
Smithsonian Astrophysical ObservatoryUNSPECIFIED
NASA Hubble FellowshipHST-HF-01233.01
NASANAS 5-26555
Subject Keywords:galaxies: dwarf; galaxies: individual (Leo IV); Local Group; stars: abundances
Issue or Number:1
Classification Code:PACS: 98.56.Wm; 97.20.Tr; 98.35.Bd; 95.85.Kr; 98.35.Ln
Record Number:CaltechAUTHORS:20100616-152157779
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Official Citation:Joshua D. Simon et al 2010 ApJ 716 446 doi: 10.1088/0004-637X/716/1/446
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:18714
Deposited By: Jason Perez
Deposited On:16 Jun 2010 22:52
Last Modified:03 Oct 2019 01:46

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