J/A+A/653/L8 Metallicities on multiple MSs of Omega Centauri (Latour+, 2021)
A stellar census in globular clusters with MUSE.
A new perspective on the multiple main sequences of Omega Centauri.
Latour M., Calamida A., Husser T.-O., Kamann S., Dreizler S., Brinchmann J.
<Astron. Astrophys. 653, L8 (2021)>
=2021A&A...653L...8L 2021A&A...653L...8L (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, globular ; Abundances, [Fe/H] ; Effective temperatures ;
Optical
Keywords: globular clusters: individual: NGC 5139 - stars: abundances -
techniques: spectroscopic
Abstract:
Omega Cen is a rare example of a globular cluster where the iron
abundance of the stars spans more than one order of magnitude. Many
spectroscopic investigations of its red-giant- and sub-giant- branches
have revealed multiple peaks in the iron abundance distribution. The
metallicity distribution of main-sequence (MS) stars is not well
characterized yet, due to the faintness of the stars and lack of data.
So far, almost all studies of MS stars are based on photometric
measurements. Our goal is to investigate the metallicity distribution
of a statistically significant sample of MS stars in Omega Cen. In
particular, we aim at revisiting the metallicity difference between
the red and blue MS of the cluster. We use MUSE spectra obtained for
the central region of omega Cen to derive metallicities for ∼4200 MS
stars. We find that blue MS stars are on average ∼0.1dex more
metal-rich than their red counterparts. On the basis of this new
estimate, we find that the two sequences can be fit on the Hubble
Space Telescope color-magnitude diagram with two isochrones having the
same global metallicity and age but a higher helium abundance for the
blue MS, i.e. {DELTA}Y~<0.1. Furthermore, we determine the average
metallicity of the five main populations along Omega Cen MS and these
estimates are consistent with expectations from previous photometric
studies.
Description:
We analyzed the MUSE spectra of selected stars on the MS of Omega
Centauri. We include the stars selected by us on the red- and blue-MS
as well as additional stars included in the 15 MSs identified by
Bellini et al., (2017, Cat. J/ApJ/844/164). We include only the stars
that have a spectrum with S/N>15. The effective temperatures and
metallicities are derived from a full spectral fit against grids of
model atmospheres computed with the PHEONIX code (Husser et al.,
2011A&A...533A...6B 2011A&A...533A...6B). We note that the model atmospheres used for the
fits are alpha-enhanced ([alpha/Fe]=0.3). Uncertainties on Teff and
M/H are calibrated as explained in the paper. Surface gravities are
derived from isochrones. Uncertainties on the log g are the standard
deviations of the log g values obtained from different isochrones (see
text in the paper for more details).
IDs and coordinates are from Bellini (2017, Cat. J/ApJ/844/164) and
the populations tags can be retrieved from Bellini et al. (2017, Cat.
J/ApJ/844/164).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tableb1.dat 71 4215 Atmospheric parameters for MS stars in omega Centauri
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See also:
J/ApJ/842/6 : Core of NGC 5139 astro-photometric catalog (Bellini+, 2017)
J/ApJ/844/164 : NGC5139 HST astro-photometric analysis. III. (Bellini+, 2017)
Byte-by-byte Description of file: tableb1.dat
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Bytes Format Units Label Explanations
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1- 6 I6 --- ID Star ID, from Bellini et al., (2017,
Cat. J/ApJ/842/6)
8- 9 I2 h RAh Right ascension (J2000)
11- 12 I2 min RAm Right ascension (J2000)
14- 19 F6.3 s RAs Right ascension (J2000)
21 A1 --- DE- Declination sign (J2000)
22- 23 I2 deg DEd Declination (J2000)
25- 26 I2 arcmin DEm Declination (J2000)
28- 32 F5.2 arcsec DEs Declination (J2000)
34- 37 I4 K Teff Effective temperature
39- 41 I3 K e_Teff Calibrated error on the effective temperature
43- 46 F4.2 [cm/s2] logg Surface gravity
48- 51 F4.2 [cm/s2] e_logg Error on the surface gravity
53- 57 F5.2 [Sun] [M/H] Metallicity
59- 62 F4.2 [Sun] e_[M/H] Calibrated error on the metallicity
64- 67 F4.1 --- SNR S/N of the spectra
69 I1 --- rMS [1]? 1 if included in our rMS
71 I1 --- bMS [1]? 1 if included in our bMS
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Acknowledgements:
Marilyn Latour, marilyn.latour(at)uni-goettingen.de
(End) Patricia Vannier [CDS] 13-Sep-2021