Article

# Globular Cluster Abundances from High-Resolution, Integrated-Light Spectroscopy. IV. The Large Magellanic Cloud: $\alpha$, Fe-peak, Light, and Heavy Elements

(Impact Factor: 5.99). 11/2011; 746(1). DOI: 10.1088/0004-637X/746/1/29
Source: arXiv

ABSTRACT

We present detailed chemical abundances in 8 clusters in the Large Magellanic
Cloud (LMC). We measure abundances of 22 elements for clusters spanning a range
in age of 0.05 to 12 Gyr, providing a comprehensive picture of the chemical
enrichment and star formation history of the LMC. The abundances were obtained
from individual absorption lines using a new method for analysis of high
resolution ($R\sim$25,000) integrated light spectra of star clusters. This
method was developed and presented in Papers I, II, and III of this series. In
this paper, we develop an additional integrated light $\chi^2$-minimization
spectral synthesis technique to facilitate measurement of weak ($\sim$15 m\AA)
spectral lines and abundances in low signal-to-noise ratio data (S/N$\sim$30).
Additionally, we supplement the integrated light abundance measurements with
detailed abundances that we measure for individual stars in the youngest
clusters (Age$<$2 Gyr) in our sample. In both the integrated light and stellar
abundances we find evolution of [$\alpha$/Fe] with [Fe/H] and age. Fe-peak
abundance ratios are similar to those in the Milky Way, with the exception of
[Cu/Fe] and [Mn/Fe], which are sub-solar at high metallicities. The heavy
elements Ba, La, Nd, Sm, and Eu are significantly enhanced in the youngest
clusters. Also, the heavy to light s-process ratio is elevated relative to the
Milky Way ([Ba/Y]$>+0.5$) and increases with decreasing age, indicating a
strong contribution of low-metallicity AGB star ejecta to the interstellar
medium throughout the later history of the LMC. We also find a correlation of
integrated light Na and Al abundances with cluster mass, in the sense that more
massive, older clusters are enriched in the light elements Na and Al with
respect to Fe, which implies that these clusters harbor star-to-star abundance
variations as is common in the Milky Way.

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Available from: Janet Colucci, Aug 08, 2014
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• "Gray points are from [12], and measured using Lick system line indexes. synthesis code [7] for the best possible accuracy in our final measurements for Ca, Si, Eu, Ba and Y. Abundances for Ba and Eu include corrections for hyperfine splitting, as described in [7]. The IL abundance analysis is described in detail in [3] [4] [5]. "
##### Article: The Detailed Chemical Abundance Patterns of M31 Globular Clusters
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ABSTRACT: We present detailed chemical abundances for $>$20 elements in $\sim$30 globular clusters in M31. These results have been obtained using high resolution ($\lambda/\Delta\lambda\sim$24,000) spectra of their integrated light and analyzed using our original method. The globular clusters have galactocentric radii between 2.5 kpc and 117 kpc, and therefore provide abundance patterns for different phases of galaxy formation recorded in the inner and outer halo of M31. We find that the clusters in our survey have a range in metallicity of $-2.2<$[Fe/H]$<-0.11$. The inner halo clusters cover this full range, while the outer halo globular clusters at R$>$20 kpc have a small range in abundance of [Fe/H]$=-1.6 \pm 0.10$. We also measure abundances of alpha, r- and s-process elements. These results constitute the first abundance pattern constraints for old populations in M31 that are comparable to those known for the Milky Way halo.
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##### Article: Comparison of Convective Overshooting Models and Their Impact on Abundances from Integrated Light Spectroscopy of Young ($<$ 3 Gyr) Star Clusters
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ABSTRACT: As part of an ongoing program to measure detailed chemical abundances in nearby galaxies, we use a sample of young to intermediate age clusters in the Large Magellanic Cloud with ages of 10 Myr to 2 Gyr to evaluate the effect of isochrone parameters, specifically core convective overshooting, on Fe abundance results from high resolution, integrated light spectroscopy. In this work we also obtain fiducial Fe abundances from high resolution spectroscopy of the cluster individual member stars. We compare the Fe abundance results for the individual stars to the results from isochrones and integrated light spectroscopy to determine whether isochrones with convective overshooting should be used in our integrated light analysis of young to intermediate age (10 Myr -3 Gyr) star clusters. We find that when using the isochrones from the Teramo group, we obtain more accurate results for young and intermediate age clusters over the entire age range when using isochrones without convective overshooting. While convective overshooting is not the only uncertain aspect of stellar evolution, it is one of the most readily parametrized ingredients in stellar evolution models, and thus important to evaluate for the specific models used in our integrated light analysis. This work demonstrates that our method for integrated light spectroscopy of star clusters can provide unique tests for future constraints on stellar evolution models of young and intermediate age clusters.
The Astrophysical Journal 02/2012; 749(2). DOI:10.1088/0004-637X/749/2/124 · 5.99 Impact Factor
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##### Article: GNOMOS: The Gemini NIR-Optical Multi Object Spectrograph
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ABSTRACT: This paper is a response to a call for white papers solicited by Gemini Observatory and its Science and Technology Advisory Committee, to help define the science case and requirements for a new Gemini instrument, envisaged to consist of a single-object spectrograph at medium resolution simultaneously covering optical and near-infrared wavelengths. In this white paper we discuss the science case for an alternative new instrument, consisting instead of a multi-object, medium-resolution, high-throughput spectrograph, covering simultaneously the optical and near-infrared slices of the electromagnetic spectrum. We argue that combination of wide wavelength coverage at medium resolution with moderate multiplexing power is an innovative path that will enable the pursuit of fundamental science questions in a variety of astrophysical topics, without compromise of the science goals achievable by single-object spectroscopy on a wide baseline. We present a brief qualitative discussion of the main features of a notional hardware design that could conceivably make such an instrument viable.