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|Title:||High-resolution CRIRES spectra of Terzan 1: a metal-poor globular cluster toward the inner bulge||Authors:||Valenti, E.
Rich, R. M.
|Issue Date:||2015||Journal:||ASTRONOMY & ASTROPHYSICS||Number:||574||First Page:||A80||Abstract:||Aims: Containing the oldest stars in the Galaxy, globular clusters toward the bulge can be used to trace its dynamical and chemical evolution. In the bulge direction, there are ~50 clusters, but only about 20% have been subject of high-resolution spectroscopic investigations. So far, the sample observed at high resolution spans a moderate-to-high metallicity regime. In this sample, however, very few are located in the innermost region (R<SUB>GC</SUB> ≤ 1.5 Kpc and | l,b | ≤ 5°). To constrain the chemical evolution enrichment of the innermost region of Galaxy, accurate abundances and abundance patterns of key elements based on high-resolution spectroscopy are necessary. Here we present the results we obtained for Terzan 1, a metal-poor cluster located in the innermost bulge region. Methods: Using the near-infrared spectrograph CRIRES at ESO/VLT, we obtained high-resolution (R ≈ 50 000) H-band spectra of 16 bright giant stars in the innermost region (r ≤ 60'') of Terzan 1. Full spectral synthesis techniques and equivalent width measurements of selected lines, isolated and free of significant blending and/or contamination by telluric lines, allowed accurate chemical abundances and radial velocities to be derived. Results: Fifteen out of 16 observed stars are likely cluster members, with an average heliocentric radial velocity of +57 ± 1.8 km s<SUP>-1</SUP> and mean iron abundance of [ Fe/H ] = -1.26 ± 0.03 dex. For these stars we measured some [α/Fe] abundance ratios, finding average values of [ O/Fe ] = +0.39 ± 0.02 dex, [ Mg/Fe ] = +0.42 ± 0.02 dex, [ Si/Fe ] = +0.31 ± 0.04 dex, and [ Ti/Fe ] = +0.15 ± 0.04 dex Conclusions: The α enhancement (≈+0.4 dex) found in the observed giant stars of Terzan 1 is consistent with previous measurements on other, more metal-rich bulge clusters, which suggests a rapid chemical enrichment. <P />Based on data taken at the ESO/VLT Telescope, within the observing program 093.D-0179(A).||Acknowledgments:||E.V. warmly thanks the telescope operators and night astronomers of Paranal working on UT1, for their competence and dedication while doing observations for this program. R.M.R. acknowledges support from grants AST-1212095, AST-1413755 from the National Science Foundation. The authors thank Ivo Saviane and Sergio Vasquez for sharing information on their results on Terzan 1 radial velocity measurements that will be presented in a forthcoming paper (Vasquez et al., in prep.). NSO/Kitt Peak FTS data used here were produced by NSF/NOAO.||URI:||http://hdl.handle.net/20.500.12386/23976||URL:||https://www.aanda.org/articles/aa/abs/2015/02/aa24888-14/aa24888-14.html||ISSN:||0004-6361||DOI:||10.1051/0004-6361/201424888||Bibcode ADS:||2015A&A...574A..80V||Fulltext:||open|
|Appears in Collections:||1.01 Articoli in rivista|
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