J/A+A/601/A96 Spectroscopy of globular clusters (Larsen+, 2017)
Detailed abundances from integrated-light spectroscopy:
Milky Way globular clusters.
Larsen S.S., Brodie J.P., Strader J.
<Astron. Astrophys. 601, A96 (2017)>
=2017A&A...601A..96L 2017A&A...601A..96L (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Clusters, globular ; Abundances, [Fe/H] ; Spectroscopy
Keywords: globular clusters: individual (NGC 104, NGC 362, NGC 6254, NGC 6388,
NGC 6752, NGC 7078, NGC 7099) -
stars: abundances - techniques: spectroscopic
Abstract:
We test the performance of our analysis technique for integrated-light
spectra by applying it to seven well-studied Galactic GCs that span a
wide range of metallicities. Integrated-light spectra were obtained by
scanning the slit of the UVES spectrograph on the ESO Very Large
Telescope across the half-light diameters of the clusters. We modelled
the spectra using resolved Hubble Space Telescope colour-magnitude
diagrams (CMDs), as well as theoretical isochrones, in combination
with standard stellar atmosphere and spectral synthesis codes. The
abundances of Fe, Na, Mg, Ca, Ti, Cr, and Ba were compared with
literature data for individual stars in the clusters. The typical
differences between iron abundances derived from our integrated-light
spectra and those compiled from the literature are less than 0.1 dex.
A larger difference is found for one cluster (NGC 6752), and is most
likely caused primarily by stochastic fluctuations in the numbers of
bright red giants within the scanned area. As expected, the
alpha-elements (Ca, Ti) are enhanced by about 0.3 dex compared to the
Solar-scaled composition, while the [Cr/Fe] ratios are close to Solar.
When using up-to-date line lists, our [Mg/Fe] ratios also agree well
with literature data. Our [Na/Fe] ratios are, on average, 0.08-0.14
dex lower than average values quoted in the literature, and our
[Ba/Fe] ratios may be overestimated by 0.20-0.35 dex at the lowest
metallicities. We find that analyses based on theoretical isochrones
give very similar results to those based on resolved CMDs.
Overall, the agreement between our integrated-light abundance
measurements and the literature data is satisfactory. Refinements of
the modelling procedure, such as corrections for stellar evolutionary
and non-LTE effects, might further reduce some of the remaining
offsets.
Description:
These tables contain the individual abundance measurements for each
cluster for our "standard" (CMD-based) analysis.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
clusters.dat 45 7 List of studied clusters
tablea1.dat 34 49 Abundances for NGC 104
tablea2.dat 34 51 Abundances for NGC 362
tablea3.dat 34 51 Abundances for NGC 6254
tablea4.dat 34 49 Abundances for NGC 6388
tablea5.dat 34 50 Abundances for NGC 6752
tablea6.dat 34 50 Abundances for NGC 7078
tablea7.dat 34 51 Abundances for NGC 7099
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Byte-by-byte Description of file: clusters.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Cluster Cluster name
11- 12 I2 h RAh Simbad right ascension (J2000.0)
14- 15 I2 min RAm Simbad right ascension (J2000.0)
17- 21 F5.2 s RAs Simbad right ascension (J2000.0)
23 A1 --- DE- Simbad declination sign (J2000.0)
24- 25 I2 deg DEd Simbad declination (J2000.0)
27- 28 I2 arcmin DEm Simbad declination (J2000.0)
30- 33 F4.1 arcsec DEs Simbad declination (J2000.0)
35- 45 A11 --- FileName Name of the table with individual abundances
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Byte-by-byte Description of file: tablea?.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- Element Element ratio
9- 14 F6.1 0.1nm lambda1 Starting wavelength of spectral window
16- 21 F6.1 0.1nm lambda2 Ending wavelength of spectral window
23- 28 F6.3 --- Abd Abundance (dex)
30- 34 F5.3 --- e_Abd Abundance error (dex)
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Acknowledgements:
Soeren Larsen, s.larsen(at)astro.ru.nl
(End) Soeren Larsen [Radboud University], Patricia Vannier [CDS] 24-Feb-2017