J/AJ/132/1630 CaII spectroscopy in Magellanic Cloud clusters (Grocholski+, 2006)
Ca II triplet spectroscopy of Large Magellanic Cloud red giants.
I. Abundances and velocities for a sample of populous clusters.
Grocholski A.J., Cole A.A., Sarajedini A., Geisler D., Smith V.V.
<Astron. J., 132, 1630-1644 (2006)>
=2006AJ....132.1630G 2006AJ....132.1630G
ADC_Keywords: Magellanic Clouds ; Associations, stellar ; Clusters, open ;
Radial velocities ; Abundances, [Fe/H]
Keywords: galaxies: star clusters - Magellanic Clouds - stars: abundances
Abstract:
Using the FORS2 instrument on the Very Large Telescope, we have
obtained near-infrared spectra for more than 200 stars in 28 populous
LMC clusters. This cluster sample spans a large range of ages
(∼113Gyr) and metallicities (-0.3≳[Fe/H]≳-2.0) and has good areal
coverage of the LMC disk. The strong absorption lines of the Ca II
triplet are used to derive cluster radial velocities and abundances.
We determine mean cluster velocities to typically 1.6km/s and mean
metallicities to 0.04dex (random error). For eight of these clusters,
we report the first spectroscopically determined metallicities based
on individual cluster stars, and six of these eight have no published
radial velocity measurements. Combining our data with archival Hubble
Space Telescope WFPC2 photometry, we find that the newly measured
cluster, NGC 1718, is one of the most metal-poor ([Fe/H]~-0.80)
intermediate-age (∼2Gyr) inner disk clusters in the LMC. Similar to
what was found by previous authors, this cluster sample has radial
velocities consistent with that of a single rotating disk system,
with no indication that the newly reported clusters exhibit halo
kinematics. In addition, our findings confirm previous results that
show that the LMC lacks the metallicity gradient typically seen in
non-barred spiral galaxies, suggesting that the bar is driving the
mixing of stellar populations in the LMC.
Description:
The spectroscopic observations were carried out with FORS2 in visitor
mode at the Antu (VLT-UT1) 8.2m telescope at ESO's Paranal Observatory
during the first half of the nights of 2004 December 21-24.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 90 29 LMC target cluster information, RV and [Fe/H]
table3.dat 61 238 Positions and measured values for all
cluster members
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See also:
J/AJ/117/238 : LMC extended catalog (Bica+, 1999)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Cluster Cluster name
11- 25 A15 --- ONames Other name(s)
27- 28 I2 h RAh Right ascension (J2000) (1)
30- 31 I2 min RAm Right ascension (J2000) (1)
33- 34 I2 s RAs Right ascension (J2000) (1)
36 A1 --- DE- Declination sign (J2000) (1)
37- 38 I2 deg DEd Declination (J2000) (1)
40- 41 I2 arcmin DEm Declination (J2000) (1)
43- 44 I2 arcsec DEs Declination (J2000) (1)
46- 48 F3.1 arcmin Diam Diameter (1)
49 A1 --- n_Diam [c] c: Estimated via comparisons with
target clusters
51- 55 F5.2 mag Vmag V magnitude (2)
57- 59 A3 --- SWB SWB type (2) (3)
60 A1 --- n_SWB [c] c: Estimated via comparisons with
target clusters
62- 66 A5 s ExpTime Exposure time
68- 69 I2 --- Nst ? Number of stars in the cluster
71- 75 F5.1 km/s RV ? Cluster radial velocity
77- 79 F3.1 km/s e_RV ? rms uncertainty on RV
81- 85 F5.2 [Sun] [Fe/H] ? Cluster metallicity
87- 90 F4.2 [Sun] e_[Fe/H] ? rms uncertainty on [Fe/H]
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Note (1): From Bica et al. (1999, Cat. J/AJ/117/238)
Note (2): From Bica et al. (1996ApJS..102...57B 1996ApJS..102...57B) unless noted
Note (3): SWB types are related to the age of the cluster, as follows:
IVB = 400-800Myr range
V = 800-2000Myr range
VI = 2000-5000Myr range
VII = 5000-16000Myr range
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Cluster Cluster name
11- 12 I2 --- ID Cluster member identification number (1)
14 I1 h RAh Hour of Right Ascension (J2000)
16- 17 I2 min RAm Minute of Right Ascension (J2000)
19- 23 F5.2 s RAs Second of Right Ascension (J2000)
25 A1 --- DE- Sign of the Declination (J2000)
26- 27 I2 deg DEd Degree of Declination (J2000)
29- 30 I2 arcmin DEm Arcminute of Declination (J2000)
32- 35 F4.1 arcsec DEs Arcsecond of Declination (J2000)
37- 41 F5.1 km/s HRV Heliocentric radial velocity
43- 45 F3.1 km/s e_HRV The 1σ error in HRV
47- 51 F5.2 mag V-VHB Brightness difference between star and
cluster's horizontal branch
53- 56 F4.2 0.1nm WCaII Summed Ca II equivalent width (2)
58- 61 F4.2 0.1nm e_WCaII The 1σ error in SigmaW
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Note (1): Stars identified as Cl* "Cluster" GCS NN in Simbad
Note (2): Where WCaII=EW(8498)+EW(8542)+EW(8662).
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Vannier [CDS] 11-Jul-2008