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J/ApJ/859/L8         Properties of TriAnd stars              (Hayes+, 2018)

Disk-like chemistry of the Triangulum-Andromeda overdensity as seen by APOGEE. Hayes C.R., Majewski S.R., Hasselquist S., Beaton R.L., Cunha K., Smith V.V., Price-Whelan A.M., Anguiano B., Beers T.C., Carrera R., Fernandez-Trincado J.G., Frinchaboy P.M., Garcia-Hernandez D.A., Lane R.R., Nidever D.L., Nitschelm C., Roman-Lopes A., Zamora O. <Astrophys. J., 859, L8 (2018)> =2018ApJ...859L...8H (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Stars, giant ; Stars, population II ; Abundances ; Positional data ; Photometry ; Radial velocities Keywords: Galaxy: disk - Galaxy: evolution - Galaxy: halo - Galaxy: structure - stars: abundances Abstract: The nature of the Triangulum-Andromeda (TriAnd) system has been debated since the discovery of this distant, low-latitude Milky Way (MW) overdensity more than a decade ago. Explanations for its origin are either as a halo substructure from the disruption of a dwarf galaxy, or a distant extension of the Galactic disk. We test these hypotheses using the chemical abundances of a dozen TriAnd members from the Sloan Digital Sky Survey-IV's (SDSS-IV's) 14th Data Release (DR14) of Apache Point Observatory Galactic Evolution Experiment (APOGEE) data to compare to APOGEE abundances of stars with similar metallicity from both the Sagittarius (Sgr) dSph and the outer MW disk. We find that TriAnd stars are chemically distinct from Sgr across a variety of elements, (C+N), Mg, K, Ca, Mn, and Ni, with a separation in [X/Fe] of about 0.1 to 0.4dex depending on the element. Instead, the TriAnd stars, with a median metallicity of about -0.8, exhibit chemical abundance ratios similar to those of the lowest metallicity ([Fe/H]~-0.7) stars in the outer Galactic disk, and are consistent with expectations of extrapolated chemical gradients in the outer disk of the MW. These results suggest that TriAnd is associated with the MW disk, and, therefore, that the disk extends to this overdensity-i.e., past a Galactocentric radius of 24kpc-albeit vertically perturbed about 7kpc below the nominal disk midplane in this region of the Galaxy. Description: Table 1 contains the properties, stellar parameters, and chemical abundances of the Triangulum-Andromeda (TriAnd) stars in reported by the Apache Point Observatory Galactic Evolution Experiment (APOGEE) in the 14th data release of the Sloan Digital Sky Survey as presented in Table 1 of Hayes et al. (2018, Cat. J/ApJ/852/49). This table also includes spectrophotometric distances from the StarHorse code presented in Queiroz et al. (2018MNRAS.476.2556Q). File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 368 12 Properties of TriAnd Stars
See also: J/ApJ/852/49 : Properties of metal-poor stars in APOGEE DR13 (Hayes+, 2018) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 18 A18 --- APOGEE APOGEE identifier (2MHHMMSSss+DDMMSSs) 20- 29 F10.6 deg RAdeg Right Ascension (J2000) 31- 39 F9.6 deg DEdeg Declination (J2000) 41- 53 F13.9 deg GLON Galactic longitude 55- 68 F14.10 deg GLAT Galactic latitude 70- 75 F6.3 mag Jmag 2MASS J band magnitude 77- 82 F6.3 mag Hmag 2MASS H band magnitude 84- 89 F6.3 mag Ksmag 2MASS Ks band magnitude 91- 99 F9.6 kpc Dist Heliocentric distance 101-112 F12.9 kpc e_Dist Uncertainty in Dist 114-122 F9.4 km/s HRV Heliocentric radial velocity 124-133 F10.8 km/s e_HRV Uncertainty in HRV 135-143 F9.4 K Teff Effective surface temperature 145-153 F9.6 K e_Teff Uncertainty in Teff 155-164 F10.8 [cm/s2] logg log surface gravity 166-176 F11.9 [cm/s2] e_logg Uncertainty in logg 178-186 F9.7 km/s Vturb Microturbulent velocity 188-196 F9.7 km/s Vmacro Macroturbulent velocity 198-208 F11.8 [Sun] [Fe/H] log Fe/H abundance 210-220 F11.9 [Sun] e_[Fe/H] Uncertainty in [Fe/H] 222-234 F13.10 [Sun] [CN/Fe] log (C+N)/Fe abundance 236-246 F11.9 [Sun] e_[CN/Fe] Uncertainty in [CN/Fe] 248-257 F10.8 [Sun] [Mg/Fe] log Mg/Fe abundance 259-269 F11.9 [Sun] e_[Mg/Fe] Uncertainty in [Mg/Fe] 271-282 F12.9 [Sun] [K/Fe] log K/Fe abundance 284-294 F11.9 [Sun] e_[K/Fe] Uncertainty in [K/Fe] 296-307 F12.9 [Sun] [Ca/Fe] log Ca/Fe abundance 309-319 F11.9 [Sun] e_[Ca/Fe] Uncertainty in [Ca/Fe] 321-332 F12.9 [Sun] [Mn/Fe] log Mn/Fe abundance 334-344 F11.9 [Sun] e_[Mn/Fe] Uncertainty in [Mn/Fe] 346-356 F11.9 [Sun] [Ni/Fe] log Ni/Fe abundance 358-368 F11.9 [Sun] e_[Ni/Fe] Uncertainty in [Ni/Fe]
Acknowledgements: Christian R. Hayes, crh7gs(at)
(End) Christian R. Hayes [Univ. Virginia], Patricia Vannier [CDS] 21-Jun-2018
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