J/A+A/554/A16 Age and metallicity relation in MC clusters (Livanou+, 2013)
Age - metallicity relation in the MCs clusters.
Livanou E., Dapergolas A., Kontizas M., Nordstroem B., Kontizas E.,
Andersen J., Dirsch B., Karampelas A.
<Astron. Astrophys. 554, A16 (2013)>
=2013A&A...554A..16L 2013A&A...554A..16L
ADC_Keywords: Magellanic Clouds ; Clusters, globular ; Photometry, uvby
Keywords: Magellanic Clouds - galaxies: abundances - galaxies: clusters: general
Abstract:
We study small open star clusters, using Stroemgren photometry to
investigate a possible dependence between age and metallicity in the
Magellanic Clouds (MCs). Our goals are to trace evidence of an age
metallicity relation (AMR) and correlate it with the mutual
interactions of the two MCs and to correlate the AMR with the spatial
distribution of the clusters. In the Large Magellanic Cloud (LMC), the
majority of the selected clusters are young (up to 1Gyr), and we
search for an AMR at this epoch, which has not been much studied. We
report results for 15 LMC and 8 Small Magellanic Cloud (SMC) clusters,
scattered all over the area of these galaxies, to cover a wide spatial
distribution and metallicity range. The selected LMC clusters were
observed with the 1.54m Danish Telescope in Chile, using the Danish
Faint Object Spectrograph and Camera (DFOSC) with a single 2kx2k CCD.
The SMC clusters were observed with the ESO 3.6m Telescope, also in
Chile, using the ESO Faint Object Spectrograph and Camera (EFOSC). The
obtained frames were analysed with the conventional DAOPHOT and IRAF
software. We used Stroemgren filters in order to achieve reliable
metallicities from photometry. Isochrone fitting was used to determine
the ages and metallicities.
The AMR for the LMC displays a metallicity gradient, with higher
metallicities for the younger ages. The AMR for LMC-SMC star clusters
shows a possible jump in metallicity and a considerable increase at
about 6x108yr. It is possible that this is connected to the latest
LMC-SMC interaction. The AMR for the LMC also displays a metallicity
gradient with distance from the centre. The metallicities in SMC are
lower, as expected for a metal-poor host galaxy.
Description:
The data set includes 15 tables for the LMC clusters, 15 tables for
the LMC clusters adjoining fields, 8 tables for the SMC clusters, and
8 tables for the SMC clusters adjoining fields. The LMC clusters were
observed with the 1.54m Danish Telescope in Chile, using the Danish
Faint Object Spectrograph and Camera (DFOSC) while the SMC clusters
were observed with the ESO 3.6m Telescope, also in Chile, using the
ESO Faint Object Spectrograph and Camera (EFOSC). The observations
took place in various intervals between December 1997 and December
2002. The photometry was derived with DAOPHOT and IRAF software.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
clusters.dat 87 23 Observing log
ages.dat 34 23 Derived ages and metallicities for 15 LMC and
the 8 SMC star clusters (table 3 of the paper)
phot/* . 46 Individual cluster and field photometry
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See also:
VII/183 : The Cluster System of the LMC (Kontizas+ 1990)
J/MNRAS/417/1559 : CT1T2 photometry in 14 SMC star clusters (Piatti+, 2011)
J/A+A/517/A50 : Ages + luminosities of SMC/LMC star clusters (Glatt+, 2010)
J/AJ/136/1703 : Ridgelines of 6 intermediate-age SMC clusters (Glatt+, 2008)
J/MNRAS/377/300 : CT1 photometry in 6 SMC star clusters (Piatti+, 2007)
J/A+A/452/179 : Ages of SMC young clusters and field stars (Chiosi+, 2006)
J/AJ/129/2701 : UBVRI photometry of SMC star clusters (Rafelski+, 2005)
J/AJ/116/723 : LMC star clusters ages and metallicity (Bica+ 1998)
J/A+AS/108/571 : Photometry of the SMC cluster NGC 330 (Vallenari+, 1994)
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 (1)
11- 13 A3 --- OName Other name
15 I1 h RAh Right ascension (J2000)
17- 18 I2 min RAm Right ascension (J2000)
20- 21 I2 s RAs Right ascension (J2000)
23 A1 --- DE- Declination sign (J2000)
24- 25 I2 deg DEd Declination (J2000)
27- 28 I2 arcmin DEm Declination (J2000)
30- 31 I2 arcsec DEs Declination (J2000)
33- 35 I3 s t.y Exposure time in y band
37- 39 I3 s t.b Exposure time in b band
41- 43 I3 s t.v Exposure time in v band
45 I1 --- Ny Number of frames in y band
47 I1 --- Nb Number of frames in b band
49 I1 --- Nv Number of frames in v band
51- 63 A13 --- Date Observation date (YYYY/MM/DD,DD)
65- 75 A11 --- File.Cl File name with cluster data in
subdirectory phot
77- 87 A11 --- File.Fld File name with cluster field data
in subdirectory phot
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Note (1): The KMHK clusters are named from Kontizas et al. 1990 (Cat. VII/183),
whereas KMK clusters are named from Kontizas et al.
(1988AJ.....96.1625K 1988AJ.....96.1625K, <KMK88 NN> in Simbad).
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Byte-by-byte Description of file: ages.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- MC LMC or SMC
5- 12 A8 --- Cluster Cluster name
14- 17 F4.2 Gyr Age Cluster age (2)
19- 22 F4.1 [Sun] [Fe/H] Metallicity (Stromgren) (2) (3)
23 A1 --- f_[Fe/H] [a] a: adopted from the Isochrones
25- 29 F5.2 [Sun] [Fe/H]I Metallicity (Isochrones) (2) (3)
31- 34 F4.2 mag E(b-y) Extinction
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Note (2): The mean errors in age and [Fe/H] are 0.4 and 0.3 respectively.
Note (3): The metallicity values are transformed from Z to [Fe/H], using the
transformation table by Durand et al. (1984ApJ...283..552D 1984ApJ...283..552D).
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Byte-by-byte Description of file(#): phot/*
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Bytes Format Units Label Explanations
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1- 8 F8.3 pix Xpos X position (1)
10- 17 F8.3 pix Ypos Y position (1)
19- 24 F6.3 mag Vmag V magnitude
26- 31 F6.3 mag e_Vmag V error
33- 38 F6.3 mag b-y b-y colour index
40- 45 F6.3 mag e_b-y b-y error
47- 52 F6.3 mag m1 Stroemgren m1 index
54- 59 F6.3 mag e_m1 Stroemgren m1 error
61- 66 F6.3 arcmin Dist Distance from the adopted cluster center
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Note (1): 1pix=0.4" for the LMC (table1-table30),
1pix=0.32" for the SMC (table31-table46).
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Acknowledgements:
Evdokia Livanou, elivanou(at)phys.uoa.gr
(End) Evdokia Livanou [NKUOA, Greece], Patricia Vannier [CDS] 28-May-2013