J/ApJ/708/1290 A 2MASS view of the Sgr dSph. VI. (Chou+, 2010)
A Two Micron All Sky Survey view of the Sagittarius dwarf galaxy.
VI. s-process and titanium abundance variations along the Sagittarius stream.
Chou M.-Y., Cunha K., Majewski S.R., Smith V.V., Patterson R.J.,
Martinez-Delgado D., Geisler D.
<Astrophys. J., 708, 1290-1309 (2010)>
=2010ApJ...708.1290C 2010ApJ...708.1290C
ADC_Keywords: Abundances ; Equivalent widths ; Stars, giant ; Stars, M-type ;
Spectroscopy
Keywords: galaxies: evolution - galaxies: individual (Sagittarius dSph) -
galaxies: interactions - Galaxy: abundances - Galaxy: halo -
stars: abundances
Abstract:
We present high-resolution spectroscopic measurements of the
abundances of the α element titanium (Ti) and s-process elements
yttrium (Y) and lanthanum (La) for 59 candidate M giant members of the
Sagittarius (Sgr) dwarf spheroidal (dSph) + tidal tail system
pre-selected on the basis of position and radial velocity (RV). As
expected, the majority of these stars show peculiar abundance patterns
compared to those of nominal Milky Way (MW) stars, but as a group, the
stars form a coherent picture of chemical enrichment of the Sgr dSph
from [Fe/H]=-1.4 to solar abundance. Finally, we analyze the chemical
abundances of a moving group of M giants among the Sgr leading arm
stars at the North Galactic Cap, but having RVs unlike the infalling
Sgr leading arm debris there. Through use of "chemical
fingerprinting," we conclude that these mostly receding northern
hemisphere M giants also are Sgr stars, likely trailing arm debris
overlapping the Sgr leading arm in the north.
Description:
Our analysis here makes use of the same spectra described in Paper V
(Chou et al., 2007, Cat. J/ApJ/670/346) for six M giant stars in the
Sgr core, 30 candidate stars in the Sgr leading arm north (LN) of the
Galactic plane, 10 in the Sgr leading arm but south of the Galactic
plane, and 13 stars in the NGC moving group, which have velocities
much higher and mostly opposite than those of the infalling Sgr
leading arm there.
The stars in our sample were observed with the 6.5m Clay telescope at
the Las Campanas Observatory and the MIKE spectrograph at R∼19000 on
the night of UT 2005 August 15, the 4m Mayall telescope echelle at
R∼35000, on the nights of UT 2004 May 5-9, at the Kitt Peak National
Observatory, and the 3.5m Telescopio Nazionale Galileo (TNG) telescope
and SARG spectrograph operating at R∼46000 in the Canary Islands, on
UT 2004 March 10-13.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 34 65 Equivalent width measurements (Ti and Y)
table3.dat 106 67 Chemical abundances for the program stars
table6.dat 40 59 Score card for the program stars
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See also:
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
J/A+A/465/815 : Abundances of Sgr dSph stars (Sbordone+, 2007)
J/ApJ/670/346 : M giant stars in the Sagittarius dwarf galaxy. V. (Chou+, 2007)
J/AJ/128/245 : M giant stars in the Sagittarius dwarf galaxy (Majewski+, 2004)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1 I1 --- Sgr [1,6] Sample (G1)
3- 16 A14 --- Name Star designation
17 A1 --- f_Name [mk] Spectrograph for HD146051 (G2)
19- 23 F5.1 --- Ti7489 ? TiIλ7489.572 equivalent width
25- 29 F5.1 --- Ti7496 ? TiIλ7496.120 equivalent width
31- 34 F4.1 --- YII YIIλ7450.320 equivalent width
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1 I1 --- Sgr [0,6] Sample (G1)
3- 16 A14 --- Name Star designation
17 A1 --- f_Name [mka] Spectrograph for HD146051 (G2)
19- 22 I4 K Teff ? Effective temperature
24- 27 F4.2 [cm/s2] logg ? Surface gravity
28- 30 A3 --- --- [(*)]? *: not explained in the paper
32- 35 F4.2 km/s xi ? Microturbulent velocity ξ
37- 40 F4.2 [-] A(Fe) Fe absolute abundance
42- 46 F5.2 [Sun] [Fe/H] ? [Fe/H] abundance ratio
48- 51 F4.2 [-] e_A(Fe) ? Standard deviation in Fe abundance
53- 54 A2 --- l_A(Ti) [CR] CR: Lines unmeasurable due to cosmic rays
or other defects
55- 58 F4.2 [-] A(Ti) ? Ti (titanium) absolute abundance
60- 64 F5.2 [Sun] [Ti/Fe] ? [Ti/Fe] abundance ratio
66- 69 F4.2 [-] e_A(Ti) ? Standard deviation in Ti abundance
71- 74 F4.2 [-] A(Y) Y (yttrium) absolute abundance
76- 80 F5.2 [Sun] [Y/Fe] ? [Y/Fe] abundance ratio
82- 85 F4.2 [-] e_A(Y) ? Standard deviation in Y abundance
87- 88 A2 --- l_A(La) [CR] CR: Lines unmeasurable due to cosmic rays
or other defects
89- 93 F5.2 [-] A(La) ? La (lanthanum) absolute abundance
94 A1 --- u_A(La) [cd] Flag on A(La) (1)
96-100 F5.2 [Sun] [La/Fe] ? [La/Fe] abundance ratio
101 A1 --- u_[La/Fe] [b] Flag on [La/Fe] (1)
103-106 F4.2 [-] e_A(La) ? Standard deviation in La abundance
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Note (1): Flag as follows:
b = Larger measurement uncertainty of La due to the noisier spectrum. These
measurements were excluded from the figures.
c = Measurement uncertain due to spectrum defect on the blue edge of the
observed La line.
d = Measurement uncertain due to unusual shape of the observed La line.
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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 I1 --- Sgr [1,5] Sample (G1)
3- 16 A14 --- Name Star designation (HHMMSSs+DDMMSS)
18- 21 F4.1 --- nTi ? Number of standard deviations for [Ti/Fe] (2)
23- 26 F4.1 --- nY ? Number of standard deviations for [Y/Fe] (2)
28- 31 F4.1 --- nLa ? Number of standard deviations for [La/Fe] (2)
33- 36 F4.1 --- Sum Sum deviation for all trends
38- 40 F3.1 --- Avg Average deviation for all three trends
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Note (2): For each of our M giants we determine the number of standard
deviations, Nσ, away from the MW (Milky Way) mean trend that
the star is at its [Fe/H] in each of the distributions shown ([Ti/Fe],
[Y/Fe], and [La/Fe] as a function of [Fe/H]; See Figure 7).
See also section 4.1 for details.
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Global notes:
Note (G1): Samples as follows:
0 = Sun
1 = Sgr core
2,3 = Sgr North leading arm (Note that in Paper V (Chou et al., 2007,
Cat. J/ApJ/670/346) we had divided the Sgr LN group into a "best" (the
fainter and farther stars that are most likely to be in the Sgr leading
arm; 2) and a "less certain" subsample (3). The latter included stars
with brighter magnitudes (Ks,0<7.5) that we considered the most
susceptible to contamination by Galactic (thick disk) stars as well as
those stars closest to the Galactic bulge. We showed in Paper V (see,
e.g., Figure 9 of that paper) that the metallicity distributions of the
"best" and "less certain" samples were similar in shape, spread, and
mean values. Further analysis of the relative abundance patterns
between these two subsamples here also reveals no obvious distinctions.
4 = Sgr South leading arm
5 = NGP: North Galactic cap moving group
6 = Standard stars
Note (G2): Spectrograph used:
m = MIKE spectrograph at the 6.5m Clay telescope at the Las Campanas Obs.
k = KPNO (Kitt Peak National Obs.)
a = average
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History:
From electronic version of the journal
References:
Majewski et al., Paper I 2003ApJ...599.1082M 2003ApJ...599.1082M
Majewski et al., Paper II 2004AJ....128..245M 2004AJ....128..245M, Cat. J/AJ/128/245
Johnson et al., Paper III 2005ApJ...619..800J 2005ApJ...619..800J
Law et al., Paper IV 2005ApJ...619..807L 2005ApJ...619..807L
Chou et al., Paper V 2007ApJ...670..346C 2007ApJ...670..346C, Cat. J/ApJ/670/346
Frinchaboy et al., Paper VII 2012ApJ...756...74F 2012ApJ...756...74F, Cat. J/ApJ/756/74
(End) Emmanuelle Perret [CDS] 21-Feb-2012