VLT/UVES Abundances in Four Nearby Dwarf Spheroidal Galaxies. II. Implications for Understanding Galaxy Evolution

By E. Tolstoy, K. Venn, M. Shetrone, F. Primas, V. Hill, A. Kaufer, T. Szeifert. 2002

227 citations recorded by the source corpus.

We have used the Ultraviolet Visual-Echelle Spectrograph (UVES) on Kueyen (UT2) of the Very Large Telescope to take spectra of 15 individual red giant stars in the centers of four nearby dwarf spheroidal galaxies (dSph's): Sculptor, Fornax, Carina, and Leo I. We measure the abundance variations of numerous elements in these low-mass stars with a range of ages (1–15 Gyr old). This means that we can effectively measure the chemical evolution of these galaxies with time. Our results show a significant spread in metallicity with age, but an overall trend consistent with what might be expected from a closed- (or perhaps leaky-) box chemical evolution scenario over the last 10–15 Gyr. We make comparisons between the properties of stars observed in dSph's and in our Galaxy's disk and halo, as well as globular cluster populations in our Galaxy and in the Large Magellanic Cloud. We also look for the signature of the earliest star formation in the universe, which may have occurred in these small systems. We notice that each of these galaxies show broadly similar abundance patterns for all elements measured. This suggests a fairly uniform progression of chemical evolution with time, despite quite a large range of star formation histories. It seems likely that these galaxies had similar initial conditions, and that they evolve in a similar manner with star formation occurring at a uniformly low rate, even if at different times. With our accurate measurements we find evidence for small variations in abundances, which seem to be correlated to variations in star formation histories between different galaxies. The α-element abundances suggest that dSph chemical evolution has not been affected by very high mass stars (>15–20 M⊙). The abundance patterns we measure for stars in dSph's are significantly different from those typically observed in the disk, bulge, and inner halo of our Galaxy. This means that, as far as we can tell from the (limited) data available to date, it is impossible to construct a significant fraction of our disk, inner halo, or bulge from stars formed in dSph's such as we see today, which subsequently merged into our own. Any merger scenario involving dSph's has to occur in the very early universe while they are still gas-rich, so the majority of mass transfer is gas and few stars.

Subfields: Astronomy and Astrophysics, Atomic and Molecular Physics, and Optics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/14c22837328f89448b885cc1fe59b100ab283821

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Citations in the corpus

“Sculptor-ing” the Galaxy? The Chemical Compositions of Red Giants in the Sculptor Dwarf Spheroidal Galaxy (2004, background): “In addition, detailed abundances are required to disentangle age from metallicity effects when attempting to derive the star formation and chemical enrichment history of Scl, as discussed by Tolstoy et al. (2003) in regard to age determinations.”
THE CHEMICAL EVOLUTION OF THE DRACO DWARF SPHEROIDAL GALAXY (2009, background): “8. dSph Galaxies and the Formation of the Galactic Halo Whether the Galactic halo could have been formed by accretion of satellite dwarf galaxies has become a question of great current interest; see e.g. Tolstoy et al (2003), Shetrone, Côté & Sargent (2001), among others.”
The stellar halo of the Galaxy (2008, methodology): “This in turn has been used to show that dwarf galaxies could not have been significant contributors of the stellar halo if accreted after they formed a significant fraction of their stars (Shetrone et al. 2001; Tolstoy et al. 2003; Venn et al. 2004).”
The Progenitors of Dwarf Spheroidal Galaxies (2002, methodology): “Recent detailed analyses of the agemetallicity evolution favor leaky-box models (e.g., Smecker-Hane & McWilliam 2003) or even closedbox models (e.g., Tolstoy et al. 2003).”
STELLAR ABUNDANCES IN THE SOLAR NEIGHBORHOOD: THE HYPATIA CATALOG (2014, result): “Our findings mimic the trends seen in Reddy et al. (2006); Pritzl et al. (2005); Tolstoy et al. (2003); Edvardsson et al. (1993), who also analyze the trends seen in [α/Fe] compared to [Fe/H] for thin- and thick-disk stars.”
Mass loss from dwarf spheroidal galaxies: the origins of shallow dark matter cores and exponential surface brightness profiles (2004, background): “If this is the case, then their stellar populations should be able to tell us much about merger histories (Tolstoy et al. 2003); their internal angular momentum and surface brightness profiles should contain vital clues as to the coupling of the gas to the dark matter in the early Universe (van den…”
Formation of isolated dwarf galaxies with feedback (2009, result): “…the minimum lifetime is increased above several hundred Myrs, the [α/Fe] ratios are too high, and there is no visible turnover point on the [α/Fe]/[Fe/H] diagram, contrary to the observed distribution of red giants in Local Group dwarf spheroidals (e.g. Shetrone et al. 2003; Tolstoy et al. 2003).”
A Comparison of Elemental Abundance Ratios in Globular Clusters, Field Stars, and Dwarf Spheroidal Galaxies (2005, background): “The detailed and recent stellar abundances in the smallest dwarf spheroidal galaxies (dSphs; Shetrone et al. 2001, 2003; Tolstoy et al. 2003; Geisler et al. 2005) have shown that their stars tend to have lower [ /Fe] abundance ratios than similar metallicity Galactic field stars.”
Resolving the Formation of Protogalaxies. II. Central Gravitational Collapse (2007, background): “Desired Improvements Clearly local dwarf spheroidals contain stars with ages consistent with formation at very high redshifts (Ferrara & Tolstoy 2000; Tolstoy et al. 2002, 2003; Helmi et al. 2006).”
The Dynamical and Chemical Evolution of Dwarf Spheroidal Galaxies with GEAR (2009, methodology): “The stellar age distributions were taken from Smecker-Hane et al. (1996); HurleyKeller et al. (1998) (Carina), Babusiaux et al. (2005); Shetrone et al. (2003); Tolstoy et al. (2003) (Sculptor), Coleman & de Jong (2008) (Fornax), and Lee et al. (2003) (Sextans).”
Λ Cold Dark Matter, Stellar Feedback, and the Galactic Halo Abundance Pattern (2005, background): “…metal abundances of dwarfs and the stellar halo is often cited as evidence against the hierarchicalΛCDM prediction (e.g. Unavane et al. 1996; Gilmore & Wyse 1998; Fulbright 2002; Tolstoy et al. 2003; Venn et al. 2004), and has even been used to argue for a revision of theΛCDM cosmology (Wyse 2004).”
A REVISED PARALLEL-SEQUENCE MORPHOLOGICAL CLASSIFICATION OF GALAXIES: STRUCTURE AND FORMATION OF S0 AND SPHEROIDAL GALAXIES (2011, background): “The α element abundances in dSph galaxies are not much enhanced with respect to solar, also consistent with prolonged star formation histories (Shetrone et al. 1998, 2001, 2003, 2009; Tolstoy et al. 2003; Venn et al. 2004; Geisler et al. 2005).”
The big problems in star formation: The star formation rate, stellar clustering, and the initial mass function (2014, background): “In principle measurements of the chemical abundance patterns in stars can provide a fourth path to measuring the IMF (e.g., Tolstoy et al. 2003; McWilliam et al. 2013).”
The Spitzer Survey of the Small Magellanic Cloud: S3MC Imaging and Photometry in the Mid- and Far-Infrared Wave Bands (2006, background): “Recentwork on dwarf spheroidal galaxies, for example, has been based on detailed spectral analyses of RGB stars (e.g., Shetrone et al. 2003; Tolstoy et al. 2003; Sadakane et al. 2004).”
Exploring Halo Substructure with Giant Stars. XI. The Tidal Tails of the Carina Dwarf Spheroidal Galaxy and the Discovery of Magellanic Cloud Stars in the Carina Foreground (2006, background): “Tolstoy et al. (2003) note that galaxy masses of order a few times 107 M⊙ — consistent with the mass of Carina derived from central velocity dispesion (Mateo et al. 1993; §4.4) — are low enough to suffer metal-enriched winds, which promote preferential depletion of metals but retention of…”
Two Distinct Ancient Components in the Sculptor Dwarf Spheroidal Galaxy: First Results from the Dwarf Abundances and Radial Velocities Team (2004, background): “There have also been studies of the abundances of small samples of individual red giant branch (RGB) stars at low and high resolution (Shetrone et al. 2003; Tolstoy et al. 2001, 2003).”