J/ApJ/759/116 Chemical analysis of NGC 4636 globular clusters (Park+, 2012)
The globular cluster system of NGC 4636 and formation of globular clusters in
giant elliptical galaxies.
Park H.S., Lee M.G., Hwang H.S., Kim S.C., Arimoto N., Yamada Y.,
Tamura N., Onodera M.
<Astrophys. J., 759, 116 (2012)>
=2012ApJ...759..116P 2012ApJ...759..116P
ADC_Keywords: Abundances ; Clusters, globular ; Spectroscopy
Keywords: galaxies: abundances; galaxies: elliptical and lenticular, cD;
galaxies: individual (NGC 4636, M87, M49, M60, NGC 5128, NGC 1399,
NGC 1407); galaxies: star clusters: general
Abstract:
We present a spectroscopic analysis of the metallicities, ages, and
alpha-elements of the globular clusters (GCs) in the giant elliptical
galaxy (gE) NGC 4636 in the Virgo Cluster. Line indices of the GCs are
measured from the integrated spectra obtained with Faint Object Camera
and Spectrograph on the Subaru 8.2m Telescope. We derive [Fe/H] values
of 59 GCs based on the Brodie & Huchra (1990ApJ...362..503B 1990ApJ...362..503B) method,
and [Z/H], age, and [α/Fe] values of 33 GCs from the comparison
of the Lick line indices with single stellar population models. The
metallicity distribution of NGC 4636 GCs shows a hint of a bimodality
with two peaks at [Fe/H]=-1.23(σ=0.32) and -0.35(σ=0.19).
The age spread is large from 2Gyr to 15Gyr and the fraction of young
GCs with age <5Gyr is about 27%. The [α/Fe] of the GCs shows a
broad distribution with a mean value [α/Fe]~0.14dex. The
dependence of these chemical properties on the galactocentric radius
is weak. We also derive the metallicities, ages, and [α/Fe]
values for the GCs in other nearby gEs (M87, M49, M60, NGC 5128,
NGC 1399, and NGC 1407) from the line index data in the literature
using the same methods as used for NGC 4636 GCs. The metallicity
distribution of GCs in the combined sample of seven gEs including
NGC 4636 is found to be bimodal, supported by the KMM test with a
significance level of >99.9%. All these gEs harbor some young GCs with
ages less than 5Gyr. The mean age of the metal-rich GCs ([Fe/H]>-0.9)
is about 3Gyr younger than that of the metal-poor GCs. The mean value
of [α/Fe] of the gE GCs is smaller than that of the Milky Way
GCs. We discuss these results in the context of GC formation in gEs.
Description:
We carried out a spectroscopic observation of GCs in NGC 4636, using
the Faint Object Camera and Spectrograph (FOCAS/MOS) at the Subaru
8.2m Telescope. Target selection, spectroscopic observation, data
reduction, and velocity measurement were described in detail in Park
et al. (2010, Cat. J/ApJ/709/377).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 101 33 Lick Line Indices (set 1)
table3.dat 93 33 Lick Line Indices (set 2)
table4.dat 101 33 Lick Index Errors (set 1)
table5.dat 93 33 Lick Index Errors (set 2)
table6.dat 117 59 Metallicity, Age, and [α/Fe] of NGC 4636
globular clusters
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See also:
J/A+A/544/A115 : Velocities of NGC 4636 globular clusters (Schuberth+, 2012)
J/ApJ/709/377 : The globular cluster system of NGC 4636 (Park+, 2010)
J/MNRAS/405/839 : Spectroscopic obs. of globular clusters (Sharina+, 2010)
J/ApJ/695/1094 : Chandra observations of NGC 4636 (Posson-Brown+, 2009)
J/A+A/459/391 : Dynamics of NGC 4636 GC system (Schuberth+, 2006)
J/A+A/433/43 : C-T1 phot. of NGC 4636 GC system (Dirsch+, 2005)
J/ApJS/116/1 : Old Stellar Populations. VI. Absorption-Line (Trager+ 1998)
J/ApJS/102/29 : Extragalactic globular clusters (Huchra+ 1996)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- ID [82/10031] Object ID Number (G1)
8- 13 F6.3 mag CN1 ? CN1 Lick line index
16- 21 F6.3 mag CN2 ? CN2 Lick line index
24- 29 F6.3 0.1nm Ca4227 ? Ca4227 Lick line index; in Angstroms
32- 37 F6.3 0.1nm G4300 ? G4300 Lick line index; in Angstroms
40- 45 F6.3 0.1nm Fe4383 ? Fe4383 Lick line index ; in Angstroms
48- 53 F6.3 0.1nm Ca4455 ? Ca4455 Lick line index; in Angstroms
56- 61 F6.3 0.1nm Fe4531 ? Fe4531 Lick line index; in Angstroms
64- 69 F6.3 0.1nm C24668 ? C24668 Lick line index; in Angstroms
72- 77 F6.3 0.1nm Hb Hβ Lick line index; in Angstroms
80- 85 F6.3 0.1nm Fe5015 Fe5015 Lick line index; in Angstroms
88- 93 F6.3 mag Mg1 Mg1 Lick line index
96-101 F6.3 mag Mg2 Mg2 Lick line index
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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- 5 I5 --- ID [82/10031] Object ID Number (G1)
8- 13 F6.3 0.1nm Mgb Mgb Lick line index; in Angstroms
16- 21 F6.3 0.1nm Fe5270 Fe5270 Lick line index; in Angstroms
24- 29 F6.3 0.1nm Fe5335 Fe5335 Lick line index; in Angstroms
32- 37 F6.3 0.1nm Fe5406 Fe5406 Lick line index; in Angstroms
40- 45 F6.3 0.1nm Fe5709 ? Fe5709 Lick line index; in Angstroms
48- 53 F6.3 0.1nm Fe5782 Fe5782 Lick line index; in Angstroms
56- 61 F6.3 0.1nm NaD NaD Lick line index; in Angstroms
64- 69 F6.3 0.1nm HdA ? HδA Lick line index; in Angstroms
72- 77 F6.3 0.1nm HgA ? HγA Lick line index; in Angstroms
80- 85 F6.3 0.1nm HdF ? HδF Lick line index; in Angstroms
88- 93 F6.3 0.1nm HgF ? HγF Lick line index; in Angstroms
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- ID Object ID Number (G1)
8- 13 F6.3 mag e_CN1 ? CN1 Lick index error
16- 21 F6.3 mag e_CN2 ? CN2 Lick index error
24- 29 F6.3 0.1nm e_Ca4227 ? Ca4227 Lick index error; in Angstroms
32- 37 F6.3 0.1nm e_G4300 ? G4300 Lick index error; in Angstroms
40- 45 F6.3 0.1nm e_Fe4383 ? Fe4383 Lick index error; in Angstroms
48- 53 F6.3 0.1nm e_Ca4455 ? Ca4455 Lick index error; in Angstroms
56- 61 F6.3 0.1nm e_Fe4531 ? Fe4531 Lick index error; in Angstroms
64- 69 F6.3 0.1nm e_C24668 ? C24668 Lick index error; in Angstroms
72- 77 F6.3 0.1nm e_Hb Hβ Lick index error; in Angstroms
80- 85 F6.3 0.1nm e_Fe5015 Fe5015 Lick index error; in Angstroms
88- 93 F6.3 mag e_Mg1 Mg1 Lick index error
96-101 F6.3 mag e_Mg2 Mg2 Lick index error
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 I5 --- ID Object ID Number (G1)
8- 13 F6.3 0.1nm e_Mgb Mgb Lick index error; in Angstroms
16- 21 F6.3 0.1nm e_Fe5270 Fe5270 Lick index error; in Angstroms
24- 29 F6.3 0.1nm e_Fe5335 Fe5335 Lick index error; in Angstroms
32- 37 F6.3 0.1nm e_Fe5406 Fe5406 Lick index error; in Angstroms
40- 45 F6.3 0.1nm e_Fe5709 ? Fe5709 Lick index error; in Angstroms
48- 53 F6.3 0.1nm e_Fe5782 Fe5782 Lick index error; in Angstroms
56- 61 F6.3 0.1nm e_NaD NaD Lick index error; in Angstroms
64- 69 F6.3 0.1nm e_HdA ? HδA Lick index error; in Angstroms
72- 77 F6.3 0.1nm e_HgA ? HγA Lick index error; in Angstroms
80- 85 F6.3 0.1nm e_HdF ? HδF Lick index error; in Angstroms
88- 93 F6.3 0.1nm e_HgF ? HγF Lick index error; in Angstroms
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- ID [82/10031] Object ID Number (G1)
8- 12 F5.2 [Sun] [Z/H]1 ? The [Z/H] derived from Hβ vs. [MgFe]'
grid method
15- 19 F5.2 [Sun] e_[Z/H]1 ? Error of [Z/H]1
22- 26 F5.2 [Sun] [Z/H]2 ? Metallicity [Z/H] derived from <Fe> vs Mg2 grid
29- 33 F5.2 [Sun] e_[Z/H]2 ? Error of [Z/H]2
36- 40 F5.1 Gyr age1 [1.8/15]? Age derived from grid method
43- 47 F5.1 Gyr e_age1 [0/5]? Error of age1
50- 54 F5.2 [Sun] [a/Fe]1 ? α-elements derived from grid method
57- 61 F5.2 [Sun] e_[a/Fe]1 ? Error of [a/Fe]
64- 68 F5.2 [Sun] [Z/H]3 ? [Z/H] derived from χ2 minimization method
71- 75 F5.2 [Sun] e_[Z/H]3 ? Error of [Z/H]3
78- 82 F5.1 Gyr age2 [1.2/15]? Age derived from χ2 minimization
method
85- 89 F5.1 Gyr e_age2 ? Error of age2
92- 96 F5.2 [Sun] [a/Fe]2 ? α-elements derived from χ2
minimization method
99-103 F5.2 [Sun] e_[a/Fe]2 ? Error of [a/Fe]2
106-110 F5.2 [Sun] [Fe/H] [-2.2/0.4] The [Fe/H] derived from Brodie and
Huchra method (1990ApJ...362..503B 1990ApJ...362..503B)
113-117 F5.2 [Sun] e_[Fe/H] Error of [Fe/H]
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Global note:
Note (G1): From Park et al. (2010, Cat. J/ApJ/709/377,
<[PLH2010] NNNNN> in Simbad).
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History:
From electronic version of the journal
References:
Park et al. RVs for NGC 4636 GCs 2010ApJ...709..377P 2010ApJ...709..377P Cat. J/ApJ/709/377
Lee et al. Kinematic analysis 2010ApJ...709.1083L 2010ApJ...709.1083L
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 15-Jul-2014