J/ApJ/746/29 High-resolution GC abundances. IV. 8 LMC GCs (Colucci+, 2012)
Globular cluster abundances from high-resolution, integrated-light spectroscopy.
IV. The Large Magellanic Cloud: α, Fe-peak, light, and heavy elements.
Colucci J.E., Bernstein R.A., Cameron S.A., McWilliam A.
<Astrophys. J., 746, 29 (2012)>
=2012ApJ...746...29C 2012ApJ...746...29C
ADC_Keywords: Clusters, globular ; Magellanic Clouds ; Abundances ;
Equivalent widths
Keywords: galaxies: abundances - galaxies: individual (LMC) -
galaxies: star clusters: general - stars: abundances -
globular clusters: individual (NGC 2005, NGC 2019, NGC 1916,
NGC 1978, NGC 1718, NGC 1866, NGC 1711, NGC 2100)
Abstract:
We present detailed chemical abundances in eight clusters in the Large
Magellanic Cloud (LMC). We measure abundances of 22 elements for
clusters spanning a range in age of 0.05-12 Gyr, providing a
comprehensive picture of the chemical enrichment and star formation
history of the LMC. The abundances were obtained from individual
absorption lines using a new method for analysis of high-resolution
(R∼25000), integrated-light (IL) spectra of star clusters. This method
was developed and presented in Papers I (2008ApJ...684..326M 2008ApJ...684..326M), II
(2009PhDT........20C 2009PhDT........20C), and III (Cat. J/ApJ/735/55) of this series. In
this paper, we develop an additional IL χ2-minimization spectral
synthesis technique to facilitate measurement of weak (∼15mÅ)
spectral lines and abundances in low signal-to-noise ratio data
(S/N∼30). Additionally, we supplement the IL abundance measurements
with detailed abundances that we measure for individual stars in the
youngest clusters (age<2Gyr) in our sample. In both the IL and stellar
abundances we find evolution of [α/Fe] with [Fe/H] and age.
Fe-peak abundance ratios are similar to those in the Milky Way (MW),
with the exception of [Cu/Fe] and [Mn/Fe], which are sub-solar at high
metallicities. The heavy elements Ba, La, Nd, Sm, and Eu are
significantly enhanced in the youngest clusters. Also, the heavy to
light s-process ratio is elevated relative to the MW ([Ba/Y]>+0.5) and
increases with decreasing age, indicating a strong contribution of
low-metallicity asymptotic giant branch star ejecta to the
interstellar medium throughout the later history of the LMC. We also
find a correlation of IL Na and Al abundances with cluster mass in the
sense that more massive, older clusters are enriched in the light
elements Na and Al with respect to Fe, which implies that these
clusters harbor star-to-star abundance variations as is common in the
MW. Lower mass, intermediate-age, and young clusters have Na and Al
abundances that are lower and more consistent with LMC field stars.
Our results can be used to constrain both future chemical evolution
models for the LMC and theories of globular cluster formation.
Description:
Integrated-light spectra for all of the LMC clusters were obtained by
uniformly scanning the core regions of each cluster. All spectra were
obtained with the 2.5m du Pont Telescope at Las Campanas in 2000
December and 2001 January, with the exception of NGC 1718 which was
observed with the MIKE double echelle spectrograph on the 6.5m
Magellan Telescope in 2006 November.
In CB11 (Colucci & Bernstein 2012ApJ...749..124C 2012ApJ...749..124C), we presented an
analysis of the [Fe/H] of 10 cool giant stars in the intermediate and
young clusters of our sample. The stellar sample includes two stars in
NGC 1978, three stars in NGC 1866, three stars in NGC 1711, and two
stars in NGC 2100. All of the stellar spectra were taken with the MIKE
spectrograph on Magellan.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 56 8 LMC cluster properties
table2.dat 86 145 Line parameters and integrated-light equivalent
widths for LMC GCs
stars.dat 37 10 Stellar targets from table 1 of 2012ApJ...749..124C 2012ApJ...749..124C
table3.dat 112 213 Line parameters and stellar equivalent widths
--------------------------------------------------------------------------------
See also:
J/ApJ/735/55 : High-resolution GCs abundances. III. LMC (Colucci+, 2011)
J/A+A/536/A60 : EROS-2 Long Period Variables in LMC (Spano+, 2011)
J/ApJ/717/277 : Chemical composition of old LMC clusters (Mucciarelli+, 2010)
J/ApJ/695/L134 : Chemical anomalies in old LMC clusters (Mucciarelli+, 2009)
J/ApJ/704/385 : M31 integrated light abundances (Colucci+, 2009)
J/AJ/136/375 : Chemical composition of LMC red giants (Mucciarelli+, 2008)
J/A+A/480/379 : Abundances of 59 red giants in LMC (Pompeia+, 2008)
J/ApJS/155/401 : Magellanic clouds GCs ISOCAM obs. (Tanabe+, 2004)
J/A+A/293/347 : LMC F supergiants (Hill+, 1995)
J/MNRAS/260/782 : CCD photometry of NGC 2004 and 2100 (Balona+ 1993)
J/ApJS/71/25 : NGC 1866 CCD photometry (Brocato+ 1989)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- Class Old(>5Gyr), Int(1-3Gyr), or Yng(<1Gyr)
5- 7 A3 --- --- [NGC]
9- 12 I4 --- NGC Cluster NGC number
14 A1 --- l_Age Limit flag on Age
15- 18 F4.2 Gyr Age Age limit or range
19 A1 --- --- [-] for a range
20- 23 F4.2 Gyr B_Age ? Upper age range
25- 29 F5.2 [Sun] [Fe/H] Metallicity
31- 35 F5.2 [Sun] B_[Fe/H] ? Upper metallicity range (if filled,
Metallicity is the lower range)
37- 40 F4.2 [Sun] e_[Fe/H] ? Uncertainty in [Fe/H]
42- 46 F5.2 [Sun] [a/Fe] ? Mean abundance of α elements (1)
48- 52 F5.2 [Sun] [a/Fe]2 ? Second value of [a/Fe] (1)
54- 56 A3 --- Ref Reference(s) (2)
--------------------------------------------------------------------------------
Note (1): Mean of [Si/Fe], [Ca/Fe], and [Ti/Fe] abundances from 1, 2, 4, and 5,
and mean of [O/Fe] from 3.
Note (2): Reference as follows:
1 = Johnson et al. 2006ApJ...640..801J 2006ApJ...640..801J;
2 = Mucciarelli et al. 2008, Cat. J/AJ/136/375;
3 = Hill et al. 2000A&A...364L..19H 2000A&A...364L..19H;
4 = Mucciarelli et al. 2011MNRAS.413..837M 2011MNRAS.413..837M;
5 = Jasniewicz & Thevenin 1994A&A...282..717J 1994A&A...282..717J
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- Ion Species identification (G1)
7- 14 F8.3 0.1nm lambda Wavelength λ (in Angstroms)
16- 20 F5.3 eV ExPot Excitation potential (G2)
22- 27 F6.3 [-] log(gf) Log of the oscillator strength
29- 34 F6.2 10-13m EW1916 ? Equivalent width for NGC 1916 (G3)
36- 41 F6.2 10-13m EW2005 ? Equivalent width for NGC 2005 (G3)
43- 48 F6.2 10-13m EW2019 ? Equivalent width for NGC 2019 (G3)
50- 54 F5.1 10-13m EW1978 ? Equivalent width for NGC 1978 (G3)
56- 61 F6.2 10-13m EW1718 ? Equivalent width for NGC 1718 (G3)
63- 67 F5.1 10-13m EW1866 ? Equivalent width for NGC 1866 (G3)
69- 72 F4.1 10-13m EW1711 ? Equivalent width for NGC 1711 (G3)
74- 78 F5.1 10-13m EW2100 ? Equivalent width for NGC 2100 (G3)
80- 86 A7 --- Type Method type (4)
--------------------------------------------------------------------------------
Note (4): Abundances that are calculated using equivalent widths are labeled
"EW" and abundances that are calculated using line synthesis are
labeled "SYN". Abundances that were calculated with hyperfine
splitting of energy levels are noted as "HFS".
--------------------------------------------------------------------------------
Byte-by-byte Description of file: stars.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 A9 --- Name Star designation
11- 18 F8.5 deg RAdeg Right ascension in decimal degrees (J2000)
20- 28 F9.5 deg DEdeg Declination in decimal degrees (J2000)
30- 33 I4 yr Obs.Y Year of observation
35- 37 A3 "month" Obs.M Month of observation
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- Ion Species identification (G1)
7- 14 F8.3 0.1nm lambda Wavelength λ (in Angstroms)
16- 20 F5.3 eV ExPot Excitation potential
22- 27 F6.3 [-] log(gf) Log of the oscillator strength (G2)
29- 33 F5.1 10-13m EW1978-737 ? Equivalent width for star 1978-737 (G3)
35 A1 --- f_EW1978-737 [S] not used for abundance (4)
37- 41 F5.1 10-13m EW1978-730 ? Equivalent width for star 1978-730 (G3)
43 A1 --- f_EW1978-730 [S] not used for abundance (4)
45- 49 F5.1 10-13m EW1866-954 ? Equivalent width for star 1866-954 (G3)
51 A1 --- f_EW1866-954 [S] not used for abundance (4)
53- 57 F5.1 10-13m EW1866-1653 ? Equivalent width for star 1866-1653(G3)
59 A1 --- f_EW1866-1653 [S] not used for abundance (4)
61- 66 F6.2 10-13m EW1866-1667 ? Equivalent width for star 1866-1667(G3)
68 A1 --- f_EW1866-1667 [S] not used for abundance (4)
70- 74 F5.1 10-13m EW1711-831 ? Equivalent width for star 1711-831 (G3)
76 A1 --- f_EW1711-831 [S] not used for abundance (4)
78- 82 F5.1 10-13m EW1711-988 ? Equivalent width for star 1711-988 (G3)
84 A1 --- f_EW1711-988 [S] not used for abundance (4)
86- 90 F5.1 10-13m EW1711-1194 ? Equivalent width for star 1711-1194 (G3)
92 A1 --- f_EW1711-1194 [S] not used for abundance (4)
94- 98 F5.1 10-13m EW2100-c12 ? Equivalent width for star 2100-c12 (G3)
100 A1 --- f_EW2100-c12 [S] not used for abundance (4)
102-106 F5.1 10-13m EW2100-b22 ? Equivalent width for star 2100-b22 (G3)
108 A1 --- f_EW2100-b22 [S] not used for abundance (4)
110-112 A3 --- Note "HFS" for hyperfine splitting (5)
--------------------------------------------------------------------------------
Note (4): Unless noted as "SYN", all abundances are calculated with the listed
equivalent widths.
Note (5): Indicates abundance calculated with hyperfine splitting of
energy levels.
--------------------------------------------------------------------------------
Global notes:
Note (G1): Lines listed twice correspond to those measured in adjacent orders
with overlapping wavelength coverage.
Note (G2): Taken from
* Paper I (2008ApJ...684..326M 2008ApJ...684..326M),
* Paper II (2009PhDT........20C 2009PhDT........20C),
* Colucci et al. (2009, Cat. J/ApJ/704/385),
* Melendez & Barbury (2009A&A...497..611M 2009A&A...497..611M) and references therein,
* Kurucz atomic and molecular line database (Kurucz 1997IAUS..189..217K 1997IAUS..189..217K).
Hyperfine line lists and A and B constants were taken from
* McWilliam & Rich (1994ApJS...91..749M 1994ApJS...91..749M),
* McWilliam et al. (1995AJ....109.2757M 1995AJ....109.2757M),
* McWilliam et al. (1995AJ....109.2736M 1995AJ....109.2736M),
* McWilliam A. (1998AJ....115.1640M 1998AJ....115.1640M),
* Johnson et al. (2006ApJ...640..801J 2006ApJ...640..801J),
* Kurucz (1997IAUS..189..217K 1997IAUS..189..217K).
Note (G3): In units of milli-Angstroms.
--------------------------------------------------------------------------------
History:
From electronic version of the journal
References:
McWilliam & Bernstein Paper I. 2008ApJ...684..326M 2008ApJ...684..326M
Cameron S.A. Paper II. 2009PhDT........20C 2009PhDT........20C
Colucci et al. M31 IL spec 2009ApJ...704..385C 2009ApJ...704..385C Cat. J/ApJ/704/385
Colucci et al. Paper III. 2011ApJ...735...55C 2011ApJ...735...55C Cat. J/ApJ/735/55
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 05-Aug-2013