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 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 2018MNRAS.476.2556Q).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 368 12 Properties of TriAnd Stars
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See also:
J/ApJ/852/49 : Properties of metal-poor stars in APOGEE DR13 (Hayes+, 2018)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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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]
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Acknowledgements:
Christian R. Hayes, crh7gs(at)virginia.edu
(End) Christian R. Hayes [Univ. Virginia], Patricia Vannier [CDS] 21-Jun-2018