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Stellar metallicities and kinematics in a gas-rich dwarf galaxy: first calcium triplet spectroscopy of red giant branch stars in WLM

Citation

Leaman, R and Cole, AA and Venn, KA and Tolstoy, E and Irwin, MJ and Szeifert, T and Skillman, ED and McConnachie, AW, Stellar metallicities and kinematics in a gas-rich dwarf galaxy: first calcium triplet spectroscopy of red giant branch stars in WLM, Astrophysical Journal, 699, (1) pp. 1-14. ISSN 0004-637X (2009) [Refereed Article]


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Copyright 2009. The American Astronomical Society

DOI: doi:10.1088/0004-637X/699/1/1

Abstract

We present the first determination of the radial velocities and metallicities of 78 red giant stars in the isolated dwarf irregular galaxy WLM. Observations of the calcium II triplet in these stars were made with FORS2 at the VLT-UT2 in two separated fields of view in WLM, and the [Fe/H] values were conformed to the Carretta & Gratton ([Fe/H]CG97) metallicity scale. The mean metallicity is 〈[Fe/H]〉 = –1.27 ± 0.04 dex, with a standard deviation of σ = 0.37. We find that the stars in the inner field are more metal-rich by Δ[Fe/H]=0.30 ± 0.06 dex. These results are in agreement with previous photometric studies that found a radial population gradient, as well as the expectation of higher metallicities in the central star-forming regions. Age estimates using Victoria-Regina stellar models show that the youngest stars in the sample (less than 6 Gyr) are more metal-rich by Δ[Fe/H]=0.32 ± 0.08 dex. These stars also show a lower velocity dispersion at all elliptical radii compared to the metal-poor stars. Kinematics for the whole red giant sample suggest a velocity gradient approximately half that of the gas rotation curve, with the stellar component occupying a thicker disk decoupled from the H I rotation plane. Taken together, the kinematics, metallicities, and ages in our sample suggest a young metal-rich, and kinematically cold stellar population in the central gas-rich regions of WLM, surrounded by a separate dynamically hot halo of older, metal-poor stars.

Item Details

Item Type:Refereed Article
Keywords:galaxies: abundances – galaxies: dwarf – galaxies: evolution – galaxies: individual (WLM) – galaxies:
Research Division:Physical Sciences
Research Group:Astronomical and Space Sciences
Research Field:Cosmology and Extragalactic Astronomy
Objective Division:Expanding Knowledge
Objective Group:Expanding Knowledge
Objective Field:Expanding Knowledge in the Physical Sciences
Author:Cole, AA (Dr Andrew Cole)
ID Code:71048
Year Published:2009
Web of Science® Times Cited:25
Deposited By:Physics
Deposited On:2011-07-07
Last Modified:2015-10-02
Downloads:193 View Download Statistics

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