J/A+A/644/A83 Jurassic structure (Fernandez-Trincado+, 2020)
Jurassic: A chemically anomalous structure in the Galactic halo.
Fernandez-Trincado J.G., Beers T.C., Minniti D.
<Astron. Astrophys. 644, A83 (2020)>
=2020A&A...644A..83F 2020A&A...644A..83F (SIMBAD/NED BibCode)
ADC_Keywords: Abundances, peculiar ; Clusters, globular ; Radial velocities ;
Spectra, infrared ; Stars, peculiar
Keywords: Galaxy: structure - Galaxy: kinematics and dynamics -
stars: chemically peculiar - globular clusters: general -
techniques: spectroscopic
Abstract:
Detailed elemental-abundance patterns of giant stars in the Galactic
halo measured by the Apache Point Observatory Galactic Evolution
Experiment (APOGEE-2) have revealed the existence of a unique and
significant stellar subpopulation of silicon-enhanced ([Si/Fe]>+0.5)
metal-poor stars, spanning a wide range of metallicities
(-1.5<[Fe/H]←0.8). Stars with over-abundances in [Si/Fe] are of great
interest because these have very strong silicon (28Si) spectral
features for stars of their metallicity and evolutionary stage,
offering clues about rare nucleosynthetic pathways in globular
clusters (GCs). Si-rich field stars have been conjectured to have been
evaporated from GCs, however, the origin of their abundances remains
unclear, and several scenarios have been offered to explain the
anomalous abundance ratios. These include the hypothesis that some of
them were born from a cloud of gas previously polluted by a progenitor
that underwent a specific and peculiar nucleosynthesis event or,
alternatively, that they were due to mass transfer from a previous
evolved companion. However, those scenarios do not simultaneously
explain the wide gamut of chemical species that are found in Si-rich
stars. Instead, we show that the present inventory of such unusual
stars, as well as their relation to known halo substructures
(including the in situ halo, Gaia-Enceladus, the Helmi Stream(s), and
Sequoia, among others), is still incomplete. We report the chemical
abundances of the iron-peak (Fe), the light- (C and N), the alpha- (O
and Mg), the odd-Z (Na and Al), and the s-process (Ce and Nd) elements
of 55 newly identified Si-rich field stars (among more than ∼600000
APOGEE-2 targets), which exhibit over-abundances of [Si/Fe] as extreme
as those observed in some Galactic GCs, and they are relatively well
distinguished from other stars in the [Si/Fe]-[Fe/H] plane. This new
census confirms the presence of a statistically significant and
chemically-anomalous structure in the inner halo: Jurassic. The
chemo-dynamical properties of the Jurassic structure is consistent
with it being the tidally disrupted remains of GCs, which are easily
distinguished by an over-abundance of [Si/Fe] among Milky Way (MW)
populations or satellites.
Description:
Basic parameters, elemental abundances, uncertainties in chemical
abundances, and orbital elements of 55 metal-poor Si-rich giant stars.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 160 55 Basic parameters of stars in the
Jurassic structure
tablea2.dat 173 55 Elemental abundances of stars in the
Jurassic structure
tablea3.dat 124 130 Uncertainties in the chemical abundances
tablea4.dat 173 52 Orbital elements of Si-rich stars
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See also:
III/284 : APOGEE-2 data from DR16 (Johnsson+, 2020)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 18 A18 --- APOGEE APOGEE identifier (APOGEE_ID)
20- 24 F5.3 mag J-Ks 2MASS J-Ks color index (JKs)
26- 33 F8.3 mag E(B-V) ?=-999 E(B-V) SFD reddening (EBV)
35- 42 F8.3 mag AKsWISE ?=-999 WISE all-sky K-band extinction
(AKs_WISE)
44- 51 F8.3 mag AKsTARG ?=-999 K-band extinction adopted for
targetting (AKs_TARG)
53- 57 F5.2 [-] [M/H] Uncalibrated [M/H] from ASPCAP analysis of
combined spectrum (MH)
59- 62 I4 K TeffASPCAP Uncalibrated ASPCAP Effective Temperature
(Teff_ASPCAP)
64- 67 F4.2 [cm/s2] loggASPCAP Uncalibrated ASPCAP Surface Gravity
(loggASPCAP)
69- 74 F6.1 K Teffph ?=-999 Photometric Effective Temperature
(Teff_pho)
76- 82 F7.2 [cm/s2] loggiso ?=-999 10Gyr PARSEC isochrone Surface
Gravity (loggiso)
84- 85 I2 --- Nvisits Number of visits for this star (Nvisits)
87- 89 I3 --- SNR Signal-to-Noise Ratio of spectrum per pixel
in APOGEE DR16 (SNR)
91- 97 F7.2 km/s RVscatter ?=-999 Radial velocity variation
(RV_SCATTER)
99-104 F6.1 km/s RV post DR16 Heliocentric radial velocity
(RV) (1)
106-111 F6.2 mas/yr pmRA* Proper motion in Right Ascension,
pmRA*cosDEC (mualphacos_delta)
113-116 F4.2 mas/yr e_pmRA* Uncertainty in mualphacos_delta
(emualphacosdelta)
118-124 F7.2 mas/yr pmDE Proper motion in Declination (mu_delta)
126-129 F4.2 mas/yr e_pmDE Uncertainty in mu_delta (emudelta)
131-137 F7.2 kpc Hdist ?=-999 Heliocentric distance (dsun)
139-145 F7.2 kpc e_Hdist ?=-999 Uncertainty in Dist (e_dsun)
147-154 A8 --- Tel Origins of the spectroscopic observations
(Telescope) (2)
156-160 F5.2 --- RUWE Renormalised Unit Weight Error (RUWE)
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Note (1): Internal released in SDSS-IV post DR16
Note (2): Origins of the spectroscopic observations as follows:
APO_2.5m = 2.5m Sloan Foundation telescope at Apache Point Observatory
in New Mexico
LCO_2.5m = 2.5m Irenee du Pont telescope at Las Campanas Observatory
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Byte-by-byte Description of file: tablea2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 18 A18 --- APOGEE APOGEE identifier (APOGEE_ID)
20- 26 F7.2 [-] [C/Fe]sp ?=-999 [C/Fe] from BACCHUS analysis of
combined spectrum (CFe_spectroscopy) (1)
28- 34 F7.2 [-] [N/Fe]sp ?=-999 [N/Fe] from BACCHUS analysis of
combined spectrum (NFe_spectroscopy) (1)
36- 42 F7.2 [-] [O/Fe]sp ?=-999 [O/Fe] from BACCHUS analysis of
combined spectrum (OFe_spectroscopy) (1)
44- 50 F7.2 [-] [Na/Fe]sp ?=-999 [Na/Fe] from BACCHUS analysis of
combined spectrum (NaFe_spectroscopy) (1)
52- 58 F7.2 [-] [Mg/Fe]sp ?=-999 [Mg/Fe] from BACCHUS analysis of
combined spectrum (MgFe_spectroscopy) (1)
60- 66 F7.2 [-] [Al/Fe]sp ?=-999 [Al/Fe] from BACCHUS analysis of
combined spectrum (AlFe_spectroscopy) (1)
68- 71 F4.2 [-] [Si/Fe]sp ?=-999 [Si/Fe] from BACCHUS analysis of
combined spectrum (SiFe_spectroscopy) (1)
73- 77 F5.2 [-] [Fe/H]sp ?=-999 [Fe/H] from BACCHUS analysis of
combined spectrum (FeH_spectroscopy) (1)
79- 85 F7.2 [-] [Ce/Fe]sp ?=-999 [Ce/Fe] from BACCHUS analysis of
combined spectrum (CeFe_spectroscopy) (1)
87- 93 F7.2 [-] [Nd/Fe]sp ?=-999 [Nd/Fe] from BACCHUS analysis of
combined spectrum (NdFe_spectroscopy) (1)
95-101 F7.2 [-] [C/Fe]ph ?=-999 [C/Fe] from BACCHUS analysis of
combined spectrum (CFe_photometry) (1)
103-109 F7.2 [-] [N/Fe]ph ?=-999 [N/Fe] from BACCHUS analysis of
combined spectrum (NFe_photometry) (1)
111-117 F7.2 [-] [O/Fe]ph ?=-999 [O/Fe] from BACCHUS analysis of
combined spectrum (OFe_photometry) (1)
119-125 F7.2 [-] [Na/Fe]ph ?=-999 [Na/Fe] from BACCHUS analysis of
combined spectrum (NaFe_photometry) (1)
127-133 F7.2 [-] [Mg/Fe]ph ?=-999 [Mg/Fe] from BACCHUS analysis of
combined spectrum (MgFe_photometry) (1)
135-141 F7.2 [-] [Al/Fe]ph ?=-999 [Al/Fe] from BACCHUS analysis of
combined spectrum (AlFe_photometry) (1)
143-149 F7.2 [-] [Si/Fe]ph ?=-999 [Si/Fe] from BACCHUS analysis of
combined spectrum (SiFe_photometry) (1)
151-157 F7.2 [-] [Fe/H]ph ?=-999 [Fe/H] from BACCHUS analysis of
combined spectrum (FeH_photometry) (1)
159-165 F7.2 [-] [Ce/Fe]ph ?=-999 [Ce/Fe] from BACCHUS analysis of
combined spectrum (CeFe_photometry) (1)
167-173 F7.2 [-] [Nd/Fe]ph ?=-999 [Nd/Fe] from BACCHUS analysis of
combined spectrum (NdFe_photometry) (1)
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Note (1): when null, value determined by adopting spectroscopic atmospheric
parameters from Table 1.
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Byte-by-byte Description of file: tablea3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 18 A18 --- APOGEE APOGEE identifier (APOGEE_ID)
20- 43 A24 [-] Errors Type of error (Errors) (1)
45- 49 F5.3 [-] e_[Fe/H] Uncertainties in [Fe/H] from BACCHUS
analysis (FeH)
51- 58 F8.3 [-] e_[C/Fe] ?=-999 Uncertainties in [C/Fe] from BACCHUS
analysis (CFe)
60- 67 F8.3 [-] e_[N/Fe] ?=-999 Uncertainties in [N/Fe] from BACCHUS
analysis (NFe)
69- 76 F8.3 [-] e_[O/Fe] ?=-999 Uncertainties in [O/Fe] from BACCHUS
analysis (OFe)
78- 82 F5.3 [-] e_[Mg/Fe] Uncertainties in [Mg/Fe] from BACCHUS
analysis (MgFe)
84- 91 F8.3 [-] e_[Al/Fe] ?=-999 Uncertainties in [Al/Fe] from BACCHUS
analysis AlFe)
93- 97 F5.3 [-] e_[Si/Fe] Uncertainties in [Si/Fe] from BACCHUS
analysis SiFe)
99-106 F8.3 [-] e_[Na/Fe] ?=-999 Uncertainties in [Na/Fe] from BACCHUS
analysis NaFe)
108-115 F8.3 [-] e_[Ce/Fe] ?=-999 Uncertainties in [Ce/Fe] from BACCHUS
analysis (CeFe)
117-124 F8.3 [-] e_[Nd/Fe] ?=-999 Uncertainties in [Nd/Fe] from BACCHUS
analysis (NdFe)
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Note (1): Types of errors as follows:
Xiabundanceerror = Final uncertainty in the abundance ratio (see Eq. 1)
sigmaXiTeff = standard deviation between the spectroscopy
Teff variation (±100 K)
sigmaXilogg = standard deviation between the spectroscopy
log(g) variation (± 0.3 dex)
sigmaXimicroturbulence = standard deviation between the microturbulence
variation (± 0.05 km/s)
sigmaXiMean = line-by-line standard deviation of the same species
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Byte-by-byte Description of file: tablea4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 18 A18 --- APOGEE APOGEE identifier(APOGEEID)
20- 23 F4.1 kpc Zmax Maximum height to the Galactic plane (Zmax)
25- 28 F4.1 kpc e_Zmax Uncertainty in Zmax (e_Zmax)
30- 33 F4.2 kpc s_Zmax Standard deviation between Zmax variation
to the bar pattern speed (std_Zmax)
35- 42 F8.6 kpc rperi Perigalactocentric distance (rperi)
44- 46 F3.1 kpc e_rperi Uncertainty in rperi (e_rperi)
48- 51 F4.2 kpc s_rperi Standard deviation between rperi variation
to the bar pattern speed (std_rperi)
53- 56 F4.1 kpc rapo Apogalactocentric distance (rapo)
58- 61 F4.1 kpc e_rapo Uncertainty in rapo (e_rapo)
63- 66 F4.2 kpc s_rapo Standard deviation between rapo variation
to the bar pattern speed (std_rapo)
68- 71 F4.2 --- ecc Orbital eccentricity (ecc)
73- 76 F4.2 --- e_ecc Uncertainty in ecc (e_ecc)
78- 81 F4.2 --- s_ecc Standard deviation between ecc variation
to the bar pattern speed (std_ecc)
83- 90 F8.1 kpc.km/s LzMIN Minimum z-component of the angular momentum
in the inertial frame (LzMIN)
92- 97 F6.1 kpc.km/s e_LzMIN Uncertainty in LzMIN (e_LzMIN)
99-104 F6.1 kpc.km/s s_LzMIN Standard deviation between LzMIN variation
to the bar pattern speed (std_LzMIN)
106-113 F8.1 kpc.km/s LzMAX Maximum z-component of the angular momentum
in the inertial frame (LzMAX)
115-120 F6.1 kpc.km/s e_LzMAX Uncertainty in LzMAX (e_LzMAX)
122-126 F5.1 kpc.km/s s_LzMAX Standard deviation between LzMAX variation
to the bar pattern speed (std_LzMAX)
128-136 F9.1 km2/s2 OrbJcst Orbital Jacobi constant
(OrbitalJacobiconstant)
138-144 F7.1 km2/s2 e_OrbJcst Uncertainty in OrbitalJacobiconstant
(eOrbitalJacobi_constant)
146-154 F9.1 km2/s2 ChaOrbE Characteristic Orbital Energy
(Characteristicorbitalenergy)
156-162 F7.1 km2/s2 e_ChaOrbE Uncertainty in Characteristicorbitalenergy
(eCharacteristicorbital_energy)
164-173 A10 --- OrbSense Orbital Sense (Orbital_Sense) (1)
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Note (1): Orbital Sense as follows:
Prograde = Prograde orbits with respect to the direction of the Galactic
rotation
Retrograde = Retrograde orbits with respect to the rotation of the bar
P-R = Orbits that change their sense of motion from prograde to
retrograde, or vice-versa as seen from the inertial frame
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Acknowledgements:
Jose G. Fernandez-Trincado, jose.fernandez(at)uda.cl
(End) Jose G. Fernandez-Trincado [UDA], Patricia Vannier [CDS] 29-Nov-2020