A Comparison of Elemental Abundance Ratios in Globular Clusters, Field Stars, and Dwarf Spheroidal Galaxies

By B. Pritzl, K. Venn, M. Irwin. 2005

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We have compiled a sample of globular clusters with high-quality stellar abundances from the literature to compare to the chemistries of stars in the Galaxy and in dwarf spheroidal galaxies. Of the 45 globular clusters examined, 29 also have kinematic information. Most of the globular clusters belong to the Galactic halo; however, a significant number have disk kinematics or belong to the bulge. Focusing on the [α/Fe] and light r-process element ratios, we find that most globular cluster stars mimic field stars of similar metallicities, and neither clearly resembles the currently available stellar abundances in dwarf galaxies (including globular clusters in the Large Magellanic Cloud). The exceptions to these general elemental ratio comparisons are already known in the literature, e.g., ω Centauri, Palomar 12, and Terzan 7 associated with the Sagittarius remnant and Ruprecht 106, which has a high radial velocity and low [α/Fe] ratio. A few other globular clusters show more marginal peculiarities. The most notable one is the halo cluster M68, which has a high galactocentric rotational velocity, a slightly younger age, and a unique [Si/Ti] ratio. The [Si/Ti] ratios decrease with increasing [Fe/H] at intermediate metallicities, which is consistent with very massive stars playing a larger role in the early chemical evolution of the Galaxy. The chemical similarities between globular clusters and field stars with [Fe/H] ≤ -1.0 suggests a shared chemical history in a well-mixed early Galaxy. The differences in the published chemistries of stars in the dwarf spheroidal galaxies suggest that neither the globular clusters, halo stars, nor thick disk stars had their origins in small isolated systems like the present-day Milky Way dwarf satellites.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/833a83f70a4d8f8747775b0e18850514b6d05079

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THE SEGUE STELLAR PARAMETER PIPELINE. II. VALIDATION WITH GALACTIC GLOBULAR AND OPEN CLUSTERS (2007, background): “A value of [Fe/H] = −2.38 was reported by Pritzl et al. (2005) from a compilation of high-quality data in the literature.”
MULTI-ELEMENT ABUNDANCE MEASUREMENTS FROM MEDIUM-RESOLUTION SPECTRA. II. CATALOG OF STARS IN MILKY WAY DWARF SATELLITE GALAXIES (2010, background): “Halo Field Stars The most metal-poor MW globular cluster known is M15 ([Fe/H] = −2.38; Sneden et al. 1997; Sneden et al. 2000; Pritzl et al. 2005).”
C, N, O abundances in the most metal-poor damped Lyman alpha systems★ (2007, background): “Such a variety of behaviours has already been seen (in other elements) in Local Group galaxies (e.g. Pritzl et al. 2005).”
Accreted versus in situ Milky Way globular clusters (2010, background): “We note that Pritzl et al. (2005) favours an extragalactic origin for NGC 4590 and Rup 106 on the basis of their peculiar alpha-element content.”
The Effective Temperatures and Physical Properties of Magellanic Cloud Red Supergiants: The Effects of Metallicity (2006, background): “Of course, the assumption that the abundances of all elements scale with a single ‘‘metallicity’’ value is a simplification but may be a good approximation: see, for example, Pritzl et al. (2005), who find that solar-like ratios of alpha-products to Fe are common even in very metal-poor systems.”
An Abundance Analysis of Bright Giants in the Globular Cluster NGC 1851 (2007, background): “The average ratio, , is rather high[Eu/Fe]p 0.71 compared with other globular clusters and field stars at the metallicity of NGC 1851 (e.g., Pritzl et al. 2005).”
THE RELATIONSHIPS AMONG COMPACT STELLAR SYSTEMS: A FRESH VIEW OF ULTRACOMPACT DWARFS (2011, background): “This is also the case for normal GCs (e.g., Pritzl et al. 2005; Woodley et al. 2010a), so the [α/Fe] implications are not yet clear.”
Stellar population models at high spectral resolution (2011, background): “…bright red giant branch stars, but these show a similar element 5 The MILES library does not contain TP-AGB star spectra hence these are not included in the TMJ fitting-function-based models abundance pattern as field stars (Pritzl et al. 2005) hence their inclusion does not affect our conclusions.”
THE ACS SURVEY OF GALACTIC GLOBULAR CLUSTERS. IX. HORIZONTAL BRANCH MORPHOLOGY AND THE SECOND PARAMETER PHENOMENON (2009, background): “Overall, the outer halo GCs’ chemical compositions remain poorly understood by comparison with the inner halo (see e.g., Pritzl et al. 2005).”
THE LEAST-LUMINOUS GALAXY: SPECTROSCOPY OF THE MILKY WAY SATELLITE SEGUE 1 (2008, result): “This is in contrast to Milky Way globular clusters which are, on average, more metal-rich and show little to no internal metallicity spread (e.g. Pritzl et al. 2005).”
Flux-calibrated stellar population models of Lick absorption-line indices with variable element abundance ratios (2010, background): “As discussed in Thomas et al. (2003, see references therein) galactic globular clusters are known to be old and α/Fe enhanced similar to halo field stars (for more recent compilations see De Angeli et al. 2005; Pritzl et al. 2005; Mendel et al. 2007).”
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.”
Properties of stellar generations in globular clusters and relations with global parameters (2010, background): “4 Similarly, Pritzl et al. (2005) adopted kinematics to assign GCs to various Galactic components; however they were able to do so only for 29 of the 45 GCs they studied.”