Disk-like Chemistry of the Triangulum-Andromeda Overdensity as Seen by APOGEE

Christian R. Hayes; Steven R. Majewski; Sten Hasselquist; Rachael L. Beaton; Katia Cunha; Verne V. Smith; Adrian M. Price-Whelan; Borja Anguiano; Timothy C. Beers; Ricardo Carrera; J. G. Fernández-Trincado; Peter M. Frinchaboy; D. A. Garcia-Hernández; Richard R. Lane; David L. Nidever; Christian Nitschelm; Alexandre Roman-Lopes; Olga Zamora

doi:10.3847/2041-8213/aac38c

Disk-like Chemistry of the Triangulum-Andromeda Overdensity as Seen by APOGEE

Christian R. Hayes, Steven R. Majewski, Sten Hasselquist, Rachael L. Beaton, Katia Cunha, Verne V. Smith, Adrian M. Price-Whelan, Borja Anguiano, Timothy C. Beers, Ricardo Carrera, J. G. Fernández-Trincado, Peter M. Frinchaboy, D. A. Garcia-Hernández, Richard R. Lane, David L. Nidever, Christian Nitschelm, Alexandre Roman-Lopes, Olga Zamora

Steward Observatory

Research output: Contribution to journal › Article › peer-review

24 Scopus citations

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 0.4 dex 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 24 kpc - albeit vertically perturbed about 7 kpc below the nominal disk midplane in this region of the Galaxy.

Original language	English (US)
Article number	L8
Journal	Astrophysical Journal Letters
Volume	859
Issue number	1
DOIs	https://doi.org/10.3847/2041-8213/aac38c
State	Published - May 20 2018

Keywords

Galaxy: disk
Galaxy: evolution
Galaxy: halo
Galaxy: structure
stars: abundances Supporting material: machine-readable table

ASJC Scopus subject areas

Astronomy and Astrophysics
Space and Planetary Science

Access to Document

10.3847/2041-8213/aac38c

Cite this

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., Fernández-Trincado, J. G., Frinchaboy, P. M., Garcia-Hernández, D. A., Lane, R. R., Nidever, D. L., Nitschelm, C., Roman-Lopes, A., & Zamora, O. (2018). Disk-like Chemistry of the Triangulum-Andromeda Overdensity as Seen by APOGEE. Astrophysical Journal Letters, 859(1), Article L8. https://doi.org/10.3847/2041-8213/aac38c

Hayes, CR, Majewski, SR, Hasselquist, S, Beaton, RL, Cunha, K, Smith, VV, Price-Whelan, AM, Anguiano, B, Beers, TC, Carrera, R, Fernández-Trincado, JG, Frinchaboy, PM, Garcia-Hernández, DA, Lane, RR, Nidever, DL, Nitschelm, C, Roman-Lopes, A & Zamora, O 2018, 'Disk-like Chemistry of the Triangulum-Andromeda Overdensity as Seen by APOGEE', Astrophysical Journal Letters, vol. 859, no. 1, L8. https://doi.org/10.3847/2041-8213/aac38c

@article{40f8b3a243df4110842052ae3e2e6477,

title = "Disk-like Chemistry of the Triangulum-Andromeda Overdensity as Seen by APOGEE",

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 0.4 dex 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 24 kpc - albeit vertically perturbed about 7 kpc below the nominal disk midplane in this region of the Galaxy.",

keywords = "Galaxy: disk, Galaxy: evolution, Galaxy: halo, Galaxy: structure, stars: abundances Supporting material: machine-readable table",

author = "Hayes, {Christian R.} and Majewski, {Steven R.} and Sten Hasselquist and Beaton, {Rachael L.} and Katia Cunha and Smith, {Verne V.} and Price-Whelan, {Adrian M.} and Borja Anguiano and Beers, {Timothy C.} and Ricardo Carrera and Fern{\'a}ndez-Trincado, {J. G.} and Frinchaboy, {Peter M.} and Garcia-Hern{\'a}ndez, {D. A.} and Lane, {Richard R.} and Nidever, {David L.} and Christian Nitschelm and Alexandre Roman-Lopes and Olga Zamora",

note = "Funding Information: Funding for the Sloan Digital Sky Survey IV has been provided by the Alfred P. Sloan Foundation, the U.S. Department of Energy Office of Science, and the Participating Institutions. SDSS-IV acknowledges support and resources from the Center for High-Performance Computing at the University of Utah. The SDSS web site ishttp://www. sdss.org. Funding Information: The authors thank the referee for helpful comments. This research used TOPCAT (Taylor 2005). C.R.H. acknowledges the NSF Graduate Research Fellowship through grant DGE-1315231. C.R.H. and S.R.M. acknowledge NSF grants AST-1312863 and AST-1616636. Support for this work was provided by NASA through Hubble Fellowship grant #51386.01 awarded to RLB by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS 5-26555 J.G.F.-T. is supported by FONDECYT No. 3180210. D.A.G.H. and O.Z. acknowledge support provided by the Spanish Ministry of Economy and Competitiveness (MINECO) under grant AYA-2017-88254-P. T.C.B. acknowledges partial support from grant PHY 14-30152 (Physics Frontier Center/JINA-CEE), awarded by the U.S. National Science Foundation. Publisher Copyright: {\textcopyright} 2018. The American Astronomical Society. All rights reserved..",

year = "2018",

month = may,

day = "20",

doi = "10.3847/2041-8213/aac38c",

language = "English (US)",

volume = "859",

journal = "Astrophysical Journal Letters",

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T1 - Disk-like Chemistry of the Triangulum-Andromeda Overdensity as Seen by APOGEE

AU - Hayes, Christian R.

AU - Majewski, Steven R.

AU - Hasselquist, Sten

AU - Beaton, Rachael L.

AU - Cunha, Katia

AU - Smith, Verne V.

AU - Price-Whelan, Adrian M.

AU - Anguiano, Borja

AU - Beers, Timothy C.

AU - Carrera, Ricardo

AU - Fernández-Trincado, J. G.

AU - Frinchaboy, Peter M.

AU - Garcia-Hernández, D. A.

AU - Lane, Richard R.

AU - Nidever, David L.

AU - Nitschelm, Christian

AU - Roman-Lopes, Alexandre

AU - Zamora, Olga

N1 - Funding Information: Funding for the Sloan Digital Sky Survey IV has been provided by the Alfred P. Sloan Foundation, the U.S. Department of Energy Office of Science, and the Participating Institutions. SDSS-IV acknowledges support and resources from the Center for High-Performance Computing at the University of Utah. The SDSS web site ishttp://www. sdss.org. Funding Information: The authors thank the referee for helpful comments. This research used TOPCAT (Taylor 2005). C.R.H. acknowledges the NSF Graduate Research Fellowship through grant DGE-1315231. C.R.H. and S.R.M. acknowledge NSF grants AST-1312863 and AST-1616636. Support for this work was provided by NASA through Hubble Fellowship grant #51386.01 awarded to RLB by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS 5-26555 J.G.F.-T. is supported by FONDECYT No. 3180210. D.A.G.H. and O.Z. acknowledge support provided by the Spanish Ministry of Economy and Competitiveness (MINECO) under grant AYA-2017-88254-P. T.C.B. acknowledges partial support from grant PHY 14-30152 (Physics Frontier Center/JINA-CEE), awarded by the U.S. National Science Foundation. Publisher Copyright: © 2018. The American Astronomical Society. All rights reserved..

PY - 2018/5/20

Y1 - 2018/5/20

N2 - 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 0.4 dex 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 24 kpc - albeit vertically perturbed about 7 kpc below the nominal disk midplane in this region of the Galaxy.

AB - 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 0.4 dex 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 24 kpc - albeit vertically perturbed about 7 kpc below the nominal disk midplane in this region of the Galaxy.

KW - Galaxy: disk

KW - Galaxy: evolution

KW - Galaxy: halo

KW - Galaxy: structure

KW - stars: abundances Supporting material: machine-readable table

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VL - 859

JO - Astrophysical Journal Letters

JF - Astrophysical Journal Letters

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ER -

Disk-like Chemistry of the Triangulum-Andromeda Overdensity as Seen by APOGEE

Abstract

Keywords

ASJC Scopus subject areas

Access to Document

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Properties of TriAnd stars

Cite this

Disk-like Chemistry of the Triangulum-Andromeda Overdensity as Seen by APOGEE

Abstract

Keywords

ASJC Scopus subject areas

Access to Document

Other files and links

Fingerprint

Datasets

Properties of TriAnd stars

Cite this