J/ApJ/872/58 Sagittarius stream stars with APOGEE obs. (Hasselquist+, 2019)
Identifying Sagittarius stream stars by their APOGEE chemical abundance
signatures.
Hasselquist S., Carlin J.L., Holtzman J.A., Shetrone M., Hayes C.R.,
Cunha K., Smith V., Beaton R.L., Sobeck J., Allende Prieto C.,
Majewski S.R., Anguiano B., Bizyaev D., Garcia-Hernandez D.A., Lane R.R.,
Pan K., Nidever D.L., Fernandez-Trincado J.G., Wilson J.C., Zamora O.
<Astrophys. J., 872, 58 (2019)>
=2019ApJ...872...58H 2019ApJ...872...58H
ADC_Keywords: Galaxies, spectra; Associations, stellar; Spectra, infrared
Keywords: galaxies: dwarf ; galaxies: individual (Sagittarius dSph) ;
galaxies: stellar content
Abstract:
The SDSS-IV Apache Point Observatory Galactic Evolution Experiment
(APOGEE) survey provides precise chemical abundances of 18 chemical
elements for ∼176000 red giant stars distributed over much of the
Milky Way Galaxy (MW), and includes observations of the core of the
Sagittarius dwarf spheroidal galaxy (Sgr). The APOGEE chemical
abundance patterns of Sgr have revealed that it is chemically distinct
from the MW in most chemical elements. We employ a k-means clustering
algorithm to six-dimensional chemical space defined by [(C+N)/Fe],
[O/Fe], [Mg/Fe], [Al/Fe], [Mn/Fe], and [Ni/Fe] to identify 62 MW stars
in the APOGEE sample that have Sgr-like chemical abundances. Of the 62
stars, 35 have Gaia kinematics and positions consistent with those
predicted by N-body simulations of the Sgr stream, and are likely
stars that have been stripped from Sgr during the last two pericenter
passages (<2Gyr ago). Another 20 of the 62 stars exhibit chemical
abundances indistinguishable from the Sgr stream stars, but are on
highly eccentric orbits with median rapo ∼25kpc. These stars are
likely the "accreted" halo population thought to be the result of a
separate merger with the MW 8-11 Gyr ago. We also find one
hypervelocity star candidate. We conclude that Sgr was enriched to
[Fe/H]~-0.2 before its most recent pericenter passage. If the
"accreted halo" population is from one major accretion event, then
this progenitor galaxy was enriched to at least [Fe/H]~-0.6, and had a
similar star formation history to Sgr before merging.
Description:
The APOGEE instrument is a high-resolution (R∼22500) near-infrared
(1.51-1.70um) spectrograph. For the main survey the instrument was
connected to the Sloan 2.5m telescope.
To identify Sgr stream stars in the APOGEE DR14 sample
(Abolfathi+ 2018ApJS..235...42A 2018ApJS..235...42A), we use the Sgr core sample from
Hasselquist+ (2017ApJ...845..162H 2017ApJ...845..162H).
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 56 62 The Sagittarius dwarf spheroidal galaxy (Sgr)
stream cluster
table2.dat 30 156 "Low-Mg" population (LMg) cluster (see Section 5.1)
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See also:
V/147 : The SDSS Photometric Catalogue, Release 12 (Alam+, 2015)
III/284 : APOGEE-2 data from DR16 (Majewski+, 2017)
I/347 : Distances to 1.33 billion stars in Gaia DR2 (Bailer-Jones+, 2018)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
J/ApJ/670/346 : M giant stars in the Sgr dwarf galaxy. V. (Chou+, 2007)
J/ApJ/749/77 : MW halo. III. Statistical abundances (Schlaufman+, 2012)
J/ApJ/779/102 : Metallicities of RGB stars in dwarf galaxies (Kirby+, 2013)
J/ApJ/778/149 : Abundances for 3 stars in Sgr dSph (McWilliam+, 2013)
J/A+A/568/A7 : Model SDSS colors for halo stars (Allende Prieto+, 2014)
J/A+A/577/A81 : Deep SDSS Optical Spectroscopy. II. (Fernandez-Alvar+, 2015)
J/ApJ/808/16 : Cannon: a new approach to determine abundances (Ness+, 2015)
J/ApJS/221/24 : SDSS-III APOGEE H-band spectral line lists (Shetrone+, 2015)
J/AJ/151/144 : ASPCAP weights for APOGEE chemical elements (Garcia+, 2016)
J/ApJ/823/59 : WISE and 2MASS photometry of M giant stars (Li+, 2016)
J/ApJ/850/96 : PS1 3π RRab stars within Sgr stream (Hernitschek+, 2017)
J/MNRAS/465/501 : APOGEE N-rich stars in inner Galaxy (Schiavon+, 2017)
J/ApJ/855/83 : Abundances of very metal-poor stars in Sgr (Hansen+, 2018)
J/ApJ/852/49 : Properties of metal-poor stars in APOGEE DR13 (Hayes+, 2018)
J/AJ/156/126 : Stellar abundances from BACCHUS analysis (Jonsson+, 2018)
J/ApJ/889/63 : Properties of Sgr Stars (Hayes+, 2020)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 18 A18 --- ID APOGEE identifier (2MHHMMSSss+DDMMSSs; J2000)
20 A1 --- Mm Membership code (1)
22- 27 F6.2 kpc Rapo [0.87/762.97] Apo-center radius
relative to the Galactic center
29- 34 F6.2 kpc E_Rapo [0.34/350.66] Upper uncertainty in Rapo
36- 41 F6.2 kpc e_Rapo [0.09/239.41] Lower uncertainty in Rapo
43- 46 F4.2 --- ecc [0.07/0.98] Eccentricity
48- 51 F4.2 --- E_ecc [0.0/0.61] Upper uncertainty in ecc
53- 56 F4.2 --- e_ecc [0.0/0.58] Lower uncertainty in ecc
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Note (1): Membership code as follows:
a = Sgr stream (35 occurrences);
b = accreted halo (20 occurrences);
c = bulge (4 occurrences);
d = hypervelocity star (HVS) -- 1 occurrence;
e = others (2 occurrences).
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 18 A18 --- ID APOGEE identifier (2MHHMMSSss+DDMMSSs; J2000)
20- 25 F6.2 kpc Rapo [0.95/110.8] Apo-center radius
relative to the Galactic center
27- 30 F4.2 --- ecc [0.09/0.99] Eccentricity
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 03-Aug-2020