J/ApJ/760/86 Equivalent widths for 13 NGC2419 RGB stars (Cohen+, 2012)
The bizarre chemical inventory of NGC 2419, an extreme outer halo globular
cluster.
Cohen J.G., Kirby E.N.
<Astrophys. J., 760, 86 (2012)>
=2012ApJ...760...86C 2012ApJ...760...86C
ADC_Keywords: Equivalent widths ; Radial velocities ; Stars, giant ;
Clusters, globular
Keywords: Galaxy: formation; Galaxy: halo;
globular clusters: individual: NGC 2419
Abstract:
We present new Keck/HIRES observations of six red giants in the
globular cluster (GC) NGC 2419. Although the cluster is among the most
distant and most luminous in the Milky Way, it was considered
chemically ordinary until very recently. Our previous work showed that
the near-infrared Ca II triplet line strength varied more than
expected for a chemically homogeneous cluster, and that at least one
star had unusual abundances of Mg and K. Here, we confirm that NGC 2419
harbors a population of stars, comprising about one-third of its mass,
that is depleted in Mg by a factor of eight and enhanced in K by a
factor of six with respect to the Mg-normal population. Although the
majority, Mg-normal population appears to have a chemical abundance
pattern indistinguishable from ordinary, inner-halo GCs, the Mg-poor
population exhibits dispersions of several elements. The abundances of
K and Sc are strongly anti-correlated with Mg, and some other elements
(Si and Ca among others) are weakly anti-correlated with Mg. These
abundance patterns suggest that the different populations of NGC 2419
sample the ejecta of diverse supernovae in addition to asymptotic
giant branch ejecta. However, the abundances of Fe-peak elements
except Sc show no star-to-star variation. We find no nucleosynthetic
source that satisfactorily explains all of the abundance variations in
this cluster. Because NGC 2419 appears like no other GC, we reiterate
our previous suggestion that it is not a GC at all, but rather the
core of an accreted dwarf galaxy.
Description:
In an effort to overcome some of the limitations of and concerns
arising from our previous work (Cohen et al. 2011, Cat. J/ApJ/740/60)
in NGC 2419, we obtained Keck/HIRES-R spectra of an additional six
stars in this globular cluster during a four-night run that began on
2012-01-29. The spectrograph configuration was identical to that which
we used in our 2008 and 2010 observations of NGC 2419 red giants.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 44 13 Data for red giant members of NGC 2419 with
Keck/HIRES spectra
table2.dat 66 279 Equivalent widths for five Mg-poor stars and
S406 in NGC 2419 with Keck/HIRES spectra
table3.dat 72 306 Equivalent widths for seven Mg-normal RGB stars
in NGC 2419 with Keck/HIRES spectra (corrected
version of the table sent by the author)
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See also:
J/MNRAS/431/1995 : Deep uVI photometry of NGC2419 (Beccari+, 2013)
J/AJ/141/81 : NGC 2419 variable star population (Di Criscienzo+, 2011)
J/ApJ/740/60 : EWs for NGC2419 and NGC7099 RGB stars (Cohen+, 2011)
J/ApJ/738/186 : HST and DEIMOS measurements of NGC 2419 stars (Ibata+, 2011)
J/ApJ/682/1217 : Abundances in red giants in 7 globular clusters (Kirby+, 2008)
J/ApJ/681/311 : Blue stragglers in NGC 2419 (Dalessandro+, 2008)
J/AJ/136/2259 : HST photometry of stars in NGC 2419 (Sandquist+, 2008)
J/PASP/117/37 : BVRI photometry in NGC 2419, Pal 4, and Pal 14 (Saha+, 2005)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- Set N=new stars or C11=Cohen et al., 2001,
Cat. J/ApJ/740/60
5- 9 A5 --- ID Star name (SNNNN) (1)
11 A1 --- n_ID Note on star (2)
13- 17 F5.2 mag Vmag [17.2/18] V-band magnitude (1)
19- 22 I4 K Teff [4265/4482] Effective temperature (3)
24- 27 F4.2 [cm/s2] logg [0.6/1.1] Surface gravity (3)
29- 33 I5 s Exp [3000/14400] Exposure time
35 A1 --- l_S/N Limit flag on S/N
36- 38 I3 --- S/N Signal to noise ratio (4)
40- 44 F5.1 km/s RV [-26.1/-16.8] Radial velocity
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Note (1): Star IDs and V magnitudes are from the online version of the database
of Stetson (2005PASP..117..563S 2005PASP..117..563S).
Note (2): Flag as follows:
d = Stetson 223 = Suntzeff 1.
e = Stetson 973 = Suntzeff 15.
f = Stetson 1209 = Suntzeff 16.
g = Stetson 1305 = RH 10 (M. Shetrone 2007, private communication),
previously observed by Shetrone et al. (2001ApJ...548..592S 2001ApJ...548..592S).
h = Stetson 1814 = Suntzeff 14.
Note (3): These values, adopted for the abundance analysis, are based only on
the V mag and an appropriate isochrone.
Note (4): S/N per spectral resolution element in the continuum at 5500Å.
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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 F7.2 0.1nm Line [4033/7797.6] Line wavelength; in Angstroms
9- 13 A5 --- Ion Species identifier
15- 18 F4.2 eV chi [0/6] Excitation potential χ
20- 25 F6.3 [-] log(gf) [-6/0.7] Log of the oscillator strength
27- 31 F5.1 10-13m S458 [10/266]? Equivalent width in S458 (mÅ)
33- 37 F5.1 10-13m S1004 ? Equivalent width in S1004 (mÅ)
40- 41 A2 --- l_S1065 [≤] Limit flag on S1065
44- 48 F5.1 10-13m S1065 ? Equivalent width in S1065 (mÅ)
50- 54 F5.1 10-13m S1131 [-11/266]? Equivalent width in S1131 (mÅ)
56- 60 F5.1 10-13m S1673 ? Equivalent width in S1673 (mÅ)
62- 66 F5.1 10-13m S406 [8/390]? Equivalent width in S406 (mÅ)
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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- 7 F7.2 0.1nm Line [3961.5/7797.6] Line wavelength; in Angstroms
9- 13 A5 --- Ion Species identifier
15- 18 F4.2 eV chi [0/6] Excitation potential χ
20- 26 F7.3 [-] log(gf) [-10.3/0.7] Log of the oscillator strength
28- 32 F5.1 10-13m S810 [5/395]? Equivalent width in S810 (mÅ)
34- 35 A2 --- l_S973 [≤] Limit flag on S973
36- 40 F5.1 10-13m S973 ? Equivalent width in S973 (mÅ)
42- 46 F5.1 10-13m S1166 ? Equivalent width in S1166 (mÅ)
48- 52 F5.1 10-13m S1209 ? Equivalent width in S1209 (mÅ)
54- 55 A2 --- l_S1305 [≤] Limit flag on S1305
56- 60 F5.1 10-13m S1305 ? Equivalent width in S1305 (mÅ)
62- 66 F5.1 10-13m S1814 [8/420]? Equivalent width in S1814 (mÅ)
68- 72 F5.1 10-13m S223 [6.7/406.8]? Equivalent width in S223 (mÅ)
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Acknowledgement:
Judy Cohen for the corrected version of table3
(column of S1814 had the equivalent widths for S223).
History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 29-Jul-2014