J/AJ/149/154 CaII spectroscopy of SMC red giants. III. (Parisi+, 2015)
Ca II triplet spectroscopy of Small Magellanic Cloud red giants.
III. Abundances and velocities for a sample of 14 clusters.
Parisi M.C., Geisler D., Claria J.J., Villanova S., Marcionni N.,
Sarajedini A., Grocholski A.J.
<Astron. J., 149, 154 (2015)>
=2015AJ....149..154P 2015AJ....149..154P
ADC_Keywords: Magellanic Clouds ; Associations, stellar ; Stars, giant ;
Equivalent widths ; Abundances, [Fe/H]
Keywords: galaxies: star clusters: general -
Magellanic Clouds; stars: abundances
Abstract:
We obtained spectra of red giants in 15 Small Magellanic Cloud (SMC)
clusters in the region of the CaII lines with FORS2 on the Very Large
Telescope. We determined the mean metallicity and radial velocity with
mean errors of 0.05dex and 2.6km/s, respectively, from a mean of 6.5
members per cluster. One cluster (B113) was too young for a reliable
metallicity determination and was excluded from the sample. We
combined the sample studied here with 15 clusters previously studied
by us using the same technique, and with 7 clusters whose
metallicities determined by other authors are on a scale similar to
ours. This compilation of 36 clusters is the largest SMC cluster
sample currently available with accurate and homogeneously determined
metallicities. We found a high probability that the metallicity
distribution is bimodal, with potential peaks at -1.1 and -0.8dex. Our
data show no strong evidence of a metallicity gradient in the SMC
clusters, somewhat at odds with recent evidence from CaII triplet
spectra of a large sample of field stars. This may be revealing
possible differences in the chemical history of clusters and field
stars. Our clusters show a significant dispersion of metallicities,
whatever age is considered, which could be reflecting the lack of a
unique age-metallicity relation in this galaxy. None of the chemical
evolution models currently available in the literature satisfactorily
represents the global chemical enrichment processes of SMC clusters.
Description:
As part of the European Southern Observatory (ESO) programs 082.B-0505
and 384.B-0687, spectra of more than ∼450 stars were obtained in
service mode. We used the FOcal Reducer and low dispersion
Spectrograph 2 (FORS2) instrument in mask exchange unit mode on the
Very Large Telescope (VLT), located at Paranal (Chile). Our
instrumental setup was identical to that used in Grocholski et al.
2006 (cat. J/AJ/132/1630) and Parisi et al. 2009 (cat. J/AJ/138/517),
wherein more detailed description can be found, in order to ensure
homogeneity.
The spectrum of each star was obtained with exposures of 680 and 635s
during the first and second observing runs, respectively. We used
slits 1" wide and between 2" and 12" long. The seeing was less than 1"
in all cases. Pixels were binned 2*2, resulting in a scale of
0.25arcsec/pixel. The spectra cover a range of ∼1500Å in the region
of the near-infrared CaII triplet (CaT; λ∼8500Å) and have a
dispersion of 0.85Å/pixel. Most cases have signal-to-noise ratio
(S/N) between ∼20 and ∼80pixel-1, with only a few stars having S/N
∼15pixel-1. Calibration exposures, bias frames and flat-fields were
also taken by the VLT staff.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 61 15 Small Magellanic Cloud (SMC) clusters sample
table2.dat 49 91 Measured values for member stars
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See also:
J/A+A/517/A50 : Ages & luminosities of SMC/LMC star clusters (Glatt+, 2010)
J/AJ/139/1168 : CaII spectroscopy of SMC fields stars (Parisi+, 2010)
J/AJ/138/517 : CaII spectroscopy of SMC red giants (Parisi+, 2009)
J/AJ/136/1039 : CaII index of SMC red giant branch stars (Carrera+, 2008)
J/AJ/132/1630 : CaII spectroscopy in Magellanic Cloud clusters
(Grocholski+, 2006)
J/A+A/440/111 : Spectra of SMC star clusters (Piatti+, 2005)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- Cluster Cluster name
9- 23 A15 --- OName Other cluster name(s)
25- 26 I2 h RAh Hour of Right Ascension (J2000)
28- 29 I2 min RAm Minute of Right Ascension (J2000)
31- 35 F5.2 s RAs Second of Right Ascension (J2000)
37 A1 --- DE- Sign of the Declination (J2000)
38- 39 I2 deg DEd Degree of Declination (J2000)
41- 42 I2 arcmin DEm Arcminute of Declination (J2000)
44- 48 F5.2 arcsec DEs Arcsecond of Declination (J2000)
50- 54 F5.3 deg a [0.5/7.6] Semimajor axis (from SMC centre)
56- 59 F4.2 Gyr Age [0.5/7.5] Age adopted
61 I1 --- r_Age [1/9] Bibliographic reference for Age (1)
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Note (1): The reference codes are defined as follows:
1 = Rafelski & Zaritsky 2005 (cat. J/AJ/129/2701);
2 = M. C. Parisi et al. (2015, in preparation);
3 = Piatti (2011MNRAS.416L..89P 2011MNRAS.416L..89P);
4 = Piatti (2011MNRAS.418L..69P 2011MNRAS.418L..69P);
5 = Glatt et al. 2008 (cat. J/AJ/136/1703);
6 = Piatti et al. 2005 (cat. J/A+A/440/111);
7 = Piatti et al. (2001MNRAS.325..792P 2001MNRAS.325..792P);
8 = Piatti et al. 2011 (cat. J/MNRAS/417/1559);
9 = Piatti et al. (cat. J/MNRAS/381/L84).
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- Cluster Cluster name
9- 10 I2 --- Star [1/33] ID for cluster member star
12- 16 F5.1 km/s HRV [103/211] Heliocentric radial velocity
18- 20 F3.1 km/s e_HRV ? The 1σ error in HRV
22- 26 F5.2 mag V-VHB [-3.28/0.03]? Brightness difference between
star and cluster's horizontal branch
28- 31 F4.2 0.1nm WCaII [4.8/9.1]? Summed CaII equivalent width
ΣW (1)
33- 36 F4.2 0.1nm e_WCaII ? The 1σ error in WCaII
38- 43 F6.3 [Sun] [Fe/H] [-1.31/-0.54]? Metallicity
45- 49 F5.3 [Sun] e_[Fe/H] ? The 1σ error in [Fe/H]
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Note (1): Where WCaII=EW(8498Å)+EW(8542Å)+EW(8662Å).
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History:
From electronic version of the journal
References:
Parisi et al., Paper I, 2009AJ....138..517P 2009AJ....138..517P, cat. J/AJ/138/517
Parisi et al., Paper II, 2010AJ....139.1168P 2010AJ....139.1168P, cat. J/AJ/139/1168
Parisi et al., Paper IV, 2016AJ....152...58P 2016AJ....152...58P, cat. J/AJ/152/58
(End) Greg Schwarz [AAS], Sylvain Guehenneux [CDS] 22-May-2015