J/ApJ/711/573 Detailed abundances in a halo stellar stream (Roederer+, 2010)
Characterizing the chemistry of the Milky Way stellar halo: detailed chemical
analysis of a metal-poor stellar stream.
Roederer I.U., Sneden C., Thompson I.B., Preston G.W., Shectman S.A.
<Astrophys. J., 711, 573-596 (2010)>
=2010ApJ...711..573R 2010ApJ...711..573R
ADC_Keywords: Equivalent widths ; Abundances ; Radial velocities ; Stars, halo ;
Stars, giant ; Milky Way
Keywords: Galaxy: halo - Galaxy: kinematics and dynamics -
nuclear reactions, nucleosynthesis, abundances - stars: abundances -
stars: kinematics and dynamics - stars: Population II
Abstract:
We present the results of a detailed abundance analysis of one of the
confirmed building blocks of the Milky Way stellar halo, a
kinematically coherent metal-poor stellar stream. We have obtained
high-resolution and high signal-to-noise spectra of 12 probable stream
members using the Magellan Inamori Kyocera Echelle spectrograph on the
Magellan-Clay Telescope at Las Campanas Observatory and the 2dCoude
spectrograph on the Smith Telescope at McDonald Observatory. We have
derived abundances or upper limits for 51 species of 46 elements in
each of these stars. The stream members show a range of metallicity
(-3.4<[Fe/H]←1.5) but are otherwise chemically homogeneous, with the
same star-to-star dispersion in [X/Fe] as the rest of the halo. This
implies that, in principle, a significant fraction of the Milky Way
stellar halo could have formed from accreted systems like the stream.
The stream stars show minimal evolution in the α or Fe-group
elements over the range of metallicity. This stream is enriched with
material produced by the main and weak components of the rapid
neutron-capture process and shows no evidence for enrichment by the
slow neutron-capture process.
Description:
Six candidate stream members were observed with the Robert G. Tull
Cross-Dispersed Echelle Spectrometer (2dCoude), located on the 2.7m
Harlan J. Smith Telescope at the McDonald Observatory, between 2009
May 06 and 2009 June 14. These spectra were taken with the 2.4"x8.0"
slit, yielding a resolving power R∼33000. An additional six candidate
stream members were observed with the Magellan Inamori Kyocera Echelle
(MIKE) spectrograph, located on the 6.5m Magellan-Clay Telescope at
Las Campanas Observatory, between 2004 June 22 and 2009 October 28.
The MIKE spectra were taken with the 0.7" wide slit, yielding a
resolving power of R∼41000 in the blue and R∼32000 in the red. See the
log of observations in table 1.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 76 24 Log of observations
table2.dat 64 12 Observational stellar data
table4.dat 44 5776 Equivalent width measurements for all stars
table5.dat 37 12 Model atmosphere parameters
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See also:
J/A+A/534/A136 : Halo red giants from the SEGUE survey (Martell+, 2011)
J/ApJ/706/1095 : Chemical compositions of 26 outer halo stars (Zhang+, 2009)
J/A+A/442/961 : Lithium content of the Galactic Halo stars (Charbonnel+, 2005)
J/A+A/415/993 : FeII, ZNI and SI abundances on halo stars (Nissen+, 2004)
J/A+A/425/671 : Equivalent widths of 10 metal-poor halo stars (Bai+, 2004)
J/AJ/125/2502 : Spectral indices of Galactic halo (Morrison+, 2003)
J/AJ/126/1362 : Century Survey Galactic Halo Project. I. (Brown+, 2003)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- Name Star name
14- 35 A22 --- Tel Telescope/Instrument
37- 40 I4 s Exp Exposure time
42- 51 A10 "YYYY/MM/DD" Obs.date Date of observation
53- 57 A5 "h:m" Obs.time UT mid-exposure
59- 69 F11.3 d HJD Heliocentric Julian Date
71- 76 F6.1 km/s HRV Heliocentric radial velocity
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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- 12 A12 --- Name Star name
14- 15 I2 h RAh Hour of right ascension (J2000)
17- 18 I2 min RAm Minute of right ascension (J2000)
20- 21 I2 s RAs Second of right ascension (J2000)
23 A1 --- DE- Sign of declination (J2000)
24- 25 I2 deg DEd Degree of declination (J2000)
27- 28 I2 arcmin DEm Arcminute of declination (J2000)
30- 31 I2 arcsec DEs Arcsecond of declination (J2000)
33- 38 F6.1 km/s HRV ? Mean or systemic heliocentric radial velocity
40 I1 --- Flag [0/3] Binarity flag (1)
42- 46 I5 s Exp Total exposure time
48 I1 --- Nobs Number of observation(s)
50- 52 I3 --- S/N3 3950Å S/N
54- 56 I3 --- S/N4 4550Å S/N
58- 60 I3 --- S/N5 5200Å S/N
62- 64 I3 --- S/N6 6750Å S/N
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Note (1): Binary flags as follows:
0 = unknown binary status;
1 = no RV variations detected in multiple epochs, either among our
observations or in combination with previous studies;
2 = RV variations detected, suspected binary, no systemic velocity listed;
3 = spectroscopic binary confirmed by other studies, systemic velocity listed.
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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- 12 A12 --- Name Object name
14- 20 F7.2 0.1nm Lambda Wavelength in Angstroms
22- 25 F4.1 --- Ion Species identification (1)
27- 30 F4.2 eV ExPot Excitation potential
32- 36 F5.2 [-] log(gf) Log of the oscillator strength
38- 42 F5.1 0.1pm EW ? Equivalent width (mÅ)
44 A1 --- f_EW [ls] Flag on EW (2)
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Note (1): The integer component of the species ID indicates the atomic
number, and the decimal component indicates the ionization state
(0 = neutral, 1 = singly ionized).
Note (2): Flag as follows:
s = abundance was derived from spectrum synthesis;
l = upper limit on the abundance.
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- Name Star name
14- 17 I4 K Teff Model effective temperature
19- 22 F4.2 [cm/s2] logg Model surface gravity
24- 27 F4.2 km/s Vt Model microturbulent velocity
29- 33 F5.2 [Sun] [M/H] Model metallicity abundance
35- 37 A3 --- State Model evolutionary state: RGB = red giant branch,
RHB = red horizontal branch,
SGB = subgiant branch.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 03-Apr-2012