J/ApJ/740/106 Abundances of 4 red giants in Pal 1 (Sakari+, 2011)
Detailed chemical abundances of four stars in the unusual globular cluster
Palomar 1.
Sakari C.M., Venn K.A., Irwin M., Aoki W., Arimoto N., Dotter A.
<Astrophys. J., 740, 106 (2011)>
=2011ApJ...740..106S 2011ApJ...740..106S
ADC_Keywords: Clusters, globular ; Equivalent widths ; Stars, giant ;
Radial velocities ; Spectroscopy
Keywords: galaxies: dwarf - globular clusters: general -
globular clusters: individual (Pal 1)
Abstract:
Detailed chemical abundances for 21 elements are presented for four
red giants in the anomalous outer halo globular cluster Palomar 1
(RGC=17.2kpc, Z=3.6kpc) using high-resolution (R=36000) spectra from
the High Dispersion Spectrograph on the Subaru Telescope. Pal 1 has
long been considered unusual because of its low surface brightness,
sparse red giant branch, young age, and its possible association with
two extragalactic streams of stars. This paper shows that its
chemistry further confirms its unusual nature. The mean metallicity of
the four stars, [Fe/H]=-0.60±0.01, is high for a globular cluster so
far from the Galactic center, but is low for a typical open cluster.
The [α/Fe] ratios, though in agreement with the Galactic stars
within the 1σ errors, agree best with the lower values in dwarf
galaxies. No signs of the Na/O anticorrelation are detected in Pal 1,
though Na appears to be marginally high in all four stars. Pal 1's
neutron-capture elements are also unusual: its high [Ba/Y] ratio
agrees best with dwarf galaxies, implying an excess of second-peak
over first-peak s-process elements, while its [Eu/α] and [Ba/Eu]
ratios show that Pal 1's contributions from the r-process must have
differed in some way from normal Galactic stars. Therefore, Pal 1 is
unusual chemically, as well in its other properties. Pal 1 shares some
of its unusual abundance characteristics with the young clusters
associated with the Sagittarius dwarf galaxy remnant and the
intermediate-age LMC clusters, and could be chemically associated with
the Canis Majoris overdensity; however, it does not seem to be similar
to the Monoceros/Galactic Anticenter Stellar Stream.
Description:
Four of our target stars are the same stars observed by Rosenberg et
al. (1998AJ....115..658R 1998AJ....115..658R): bright, RGB stars, with radial velocities
that make them likely cluster members. We refer to these stars as Pal
1-I, -II, -III, and -IV. The bright object located at the center of
the cluster, Pal 1-C, was also included as a target, although the
membership of this object is not as certain as the others.
In addition to the Pal 1 stars, we include an analysis of a "standard"
star, M67-141 (as identified by Fagerholm 1906PhDT.........1F 1906PhDT.........1F). This
star resides in the metal-rich open cluster M67.
These stars were observed on several runs in 2006 January and 2007
January using the High Dispersion Spectrograph (HDS) on the 8.2m
Subaru Telescope.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 60 6 Our target stars, their positions and magnitudes
table2.dat 61 6 Observations and calculated heliocentric radial
velocities
table3.dat 73 378 The line list
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See also:
B/hst : HST Archived Exposures Catalog (STScI, 2007)
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
I/259 : The Tycho-2 Catalogue (Hog+ 2000)
VII/151 : Structure Parameters of Galactic Globular Clusters (Webbink 1985)
J/A+A/525/A124 : Pal1-I elemental EWs and abundances (Monaco+, 2011)
J/MNRAS/396/1075 : GCs in nearby dwarf galaxies. II (Georgiev+, 2009)
J/A+A/450/105 : Properties of 153 Galactic globular clusters (Bica+, 2006)
J/MNRAS/365/1357 : Absolute magnitude of GCs (Di Criscienzo+, 2006)
J/A+A/359/347 : Reddening in open and globular clusters (Dutra+, 2000)
J/A+AS/110/1 : CCD photometry of Pal 1 (Borissova+ 1995)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Star Star designation (1)
11 I1 h RAh Hour of right ascension (J2000) (1)
13- 14 I2 min RAm Minute of right ascension (J2000)
16- 19 F4.1 s RAs Second of right ascension (J2000)
21 A1 --- DE- Sign of declination (J2000) (1)
22- 23 I2 deg DEd Degree of declination (J2000)
25- 26 I2 arcmin DEm Arcminute of declination (J2000)
28- 31 F4.1 arcsec DEs Arcsecond of declination (J2000)
33- 38 F6.3 mag Vmag V-band magnitude (2)
40- 45 F6.3 mag Imag I-band magnitude (2)
47- 52 F6.3 mag Ksmag 2MASS (Cat. II/246) Ks-band magnitude
54- 60 A7 --- Ref Reference(s) (3)
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Note (1): Note that Pal1-I coordinates are more likely 3 33 21.83 +79 35 38.2
(see 2MASS Ks magnitude and figure 2) than 3 33 21.8 +79 35 16.2;
position corrected at CDS.
Note (2): M67-141 V and I magnitudes are in the Kron-Cousins system, while the
Pal 1 V and I magnitudes have been transformed to the Johnson system
from the HST system.
Note (3): Reference as follows:
1 = Hog et al. 2000, Cat. I/259;
2 = Sanders 1977A&AS...27...89S 1977A&AS...27...89S;
3 = Janes & Smith 1984AJ.....89..487J 1984AJ.....89..487J;
4 = Sarajedini et al. 2007AJ....133.1658S 2007AJ....133.1658S
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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- 9 A9 --- Star Star designation
11- 21 A11 "YYYY/MMM/DD" Date First observation date
23- 27 A5 --- Dates Second and third days of observation
29- 33 I5 s Exp Exposure time
35- 37 I3 --- S/N53 ? Signal to noise ratio per resolution
element at 5310Å
38 A1 --- f_S/N53 [b] Flag on Pal 1-IV (4)
40- 42 I3 --- S/N66 ? Signal to noise ratio per resolution
element at 6616Å
43 A1 --- f_S/N66 [b] Flag on Pal 1-IV (4)
45- 49 F5.1 km/s HRV Heliocentric radial velocity
51- 53 F3.1 km/s e_HRV HRV uncertainty
55- 61 A7 --- Lbl Star as labelled in table 3 (column
added by CDS)
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Note (4):
b = Pal 1-IV was dropped from the analysis, as the seeing was too poor to
perform a sky subtraction.
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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 lambda Spectral line wavelength; in Angstroms
9- 12 A4 --- El Element and ionization state
14- 17 F4.2 eV ExPot Excitation Potential
19- 25 F7.3 --- loggf Log of the oscillator strength
27- 31 F5.1 10-13m SunEW ? Equivalent width in the Sun (mÅ)
33 A1 --- f_SunEW [S] Spectrum Synthesis Flag on SunEW
35- 39 F5.1 10-13m M67141EW ? Equivalent width in the M67-141 (mÅ)
41 A1 --- f_M67141EW [S] Spectrum Synthesis Flag on M67141EW
43- 47 F5.1 10-13m Pal1IEW ? Equivalent width in the Pal 1-I (mÅ)
49 A1 --- f_Pal1IEW [S] Spectrum Synthesis Flag on Pal1IEW
51- 55 F5.1 10-13m Pal1IIEW ? Equivalent width in the Pal 1-II (mÅ)
57 A1 --- f_Pal1IIEW [S] Spectrum Synthesis Flag on Pal1IIEW
59- 63 F5.1 10-13m Pal1IIIEW ? Equivalent width in the Pal 1-III (mÅ)
65 A1 --- f_Pal1IIIEW [S] Spectrum Synthesis Flag on Pal1IIIEW
67- 71 F5.1 10-13m Pal1CEW ? Equivalent width in the Pal 1-C (mÅ)
73 A1 --- f_Pal1CEW [S] Spectrum Synthesis Flag on Pal1CEW
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 12-Feb-2013