The Galah Survey: Classification and Diagnostics with t-SNE Reduction of Spectral Information

G. Traven, G. Matijevič, T. Zwitter, M. Žerjal, J. Kos, M. Asplund, J. Bland-Hawthorn, A. R. Casey, G. De Silva, K. Freeman, J. Lin, S. L. Martell, K. J. Schlesinger, S. Sharma, J. D. Simpson, D. B. Zucker, B. Anguiano, G. Da Costa, L. Duong, J. Horner & 7 others E. A. Hyde, P. R. Kafle, U. Munari, D. Nataf, C. A. Navin, W. Reid, Y. S. Ting

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

Galah is an ongoing high-resolution spectroscopic survey with the goal of disentangling the formation history of the Milky Way using the fossil remnants of disrupted star formation sites that are now dispersed around the Galaxy. It is targeting a randomly selected magnitude-limited (V ≤ 14) sample of stars, with the goal of observing one million objects. To date, 300,000 spectra have been obtained. Not all of them are correctly processed by parameter estimation pipelines, and we need to know about them. We present a semi-automated classification scheme that identifies different types of peculiar spectral morphologies in an effort to discover and flag potentially problematic spectra and thus help to preserve the integrity of the survey results. To this end, we employ the recently developed dimensionality reduction technique t-SNE (t-distributed stochastic neighbor embedding), which enables us to represent the complex spectral morphology in a two-dimensional projection map while still preserving the properties of the local neighborhoods of spectra. We find that the majority (178,483) of the 209,533 Galah spectra considered in this study represents normal single stars, whereas 31,050 peculiar and problematic spectra with very diverse spectral features pertaining to 28,579 stars are distributed into 10 classification categories: hot stars, cool metal-poor giants, molecular absorption bands, binary stars, Hμ/Hβ emission, Hμ/Hβ emission superimposed on absorption, Hμ/Hβ P-Cygni, Hμ/Hβ inverted P-Cygni, lithium absorption, and problematic. Classified spectra with supplementary information are presented in the catalog, indicating candidates for follow-up observations and population studies of the short-lived phases of stellar evolution.

Original languageEnglish
Article number24
JournalAstrophysical Journal, Supplement Series
Volume228
Issue number2
DOIs
Publication statusPublished - 23 Feb 2017

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embedding
stars
molecular absorption
hot stars
stellar evolution
binary stars
fossils
lithium
integrity
preserving
targeting
catalogs
star formation
projection
histories
fossil
galaxies
absorption spectra
high resolution
metal

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Traven, G., Matijevič, G., Zwitter, T., Žerjal, M., Kos, J., Asplund, M., ... Ting, Y. S. (2017). The Galah Survey: Classification and Diagnostics with t-SNE Reduction of Spectral Information. Astrophysical Journal, Supplement Series, 228(2), [24]. https://doi.org/10.3847/1538-4365/228/2/24
Traven, G. ; Matijevič, G. ; Zwitter, T. ; Žerjal, M. ; Kos, J. ; Asplund, M. ; Bland-Hawthorn, J. ; Casey, A. R. ; De Silva, G. ; Freeman, K. ; Lin, J. ; Martell, S. L. ; Schlesinger, K. J. ; Sharma, S. ; Simpson, J. D. ; Zucker, D. B. ; Anguiano, B. ; Da Costa, G. ; Duong, L. ; Horner, J. ; Hyde, E. A. ; Kafle, P. R. ; Munari, U. ; Nataf, D. ; Navin, C. A. ; Reid, W. ; Ting, Y. S. / The Galah Survey : Classification and Diagnostics with t-SNE Reduction of Spectral Information. In: Astrophysical Journal, Supplement Series. 2017 ; Vol. 228, No. 2.
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Traven, G, Matijevič, G, Zwitter, T, Žerjal, M, Kos, J, Asplund, M, Bland-Hawthorn, J, Casey, AR, De Silva, G, Freeman, K, Lin, J, Martell, SL, Schlesinger, KJ, Sharma, S, Simpson, JD, Zucker, DB, Anguiano, B, Da Costa, G, Duong, L, Horner, J, Hyde, EA, Kafle, PR, Munari, U, Nataf, D, Navin, CA, Reid, W & Ting, YS 2017, 'The Galah Survey: Classification and Diagnostics with t-SNE Reduction of Spectral Information' Astrophysical Journal, Supplement Series, vol. 228, no. 2, 24. https://doi.org/10.3847/1538-4365/228/2/24

The Galah Survey : Classification and Diagnostics with t-SNE Reduction of Spectral Information. / Traven, G.; Matijevič, G.; Zwitter, T.; Žerjal, M.; Kos, J.; Asplund, M.; Bland-Hawthorn, J.; Casey, A. R.; De Silva, G.; Freeman, K.; Lin, J.; Martell, S. L.; Schlesinger, K. J.; Sharma, S.; Simpson, J. D.; Zucker, D. B.; Anguiano, B.; Da Costa, G.; Duong, L.; Horner, J.; Hyde, E. A.; Kafle, P. R.; Munari, U.; Nataf, D.; Navin, C. A.; Reid, W.; Ting, Y. S.

In: Astrophysical Journal, Supplement Series, Vol. 228, No. 2, 24, 23.02.2017.

Research output: Contribution to journalArticle

TY - JOUR

T1 - The Galah Survey

T2 - Classification and Diagnostics with t-SNE Reduction of Spectral Information

AU - Traven, G.

AU - Matijevič, G.

AU - Zwitter, T.

AU - Žerjal, M.

AU - Kos, J.

AU - Asplund, M.

AU - Bland-Hawthorn, J.

AU - Casey, A. R.

AU - De Silva, G.

AU - Freeman, K.

AU - Lin, J.

AU - Martell, S. L.

AU - Schlesinger, K. J.

AU - Sharma, S.

AU - Simpson, J. D.

AU - Zucker, D. B.

AU - Anguiano, B.

AU - Da Costa, G.

AU - Duong, L.

AU - Horner, J.

AU - Hyde, E. A.

AU - Kafle, P. R.

AU - Munari, U.

AU - Nataf, D.

AU - Navin, C. A.

AU - Reid, W.

AU - Ting, Y. S.

PY - 2017/2/23

Y1 - 2017/2/23

N2 - Galah is an ongoing high-resolution spectroscopic survey with the goal of disentangling the formation history of the Milky Way using the fossil remnants of disrupted star formation sites that are now dispersed around the Galaxy. It is targeting a randomly selected magnitude-limited (V ≤ 14) sample of stars, with the goal of observing one million objects. To date, 300,000 spectra have been obtained. Not all of them are correctly processed by parameter estimation pipelines, and we need to know about them. We present a semi-automated classification scheme that identifies different types of peculiar spectral morphologies in an effort to discover and flag potentially problematic spectra and thus help to preserve the integrity of the survey results. To this end, we employ the recently developed dimensionality reduction technique t-SNE (t-distributed stochastic neighbor embedding), which enables us to represent the complex spectral morphology in a two-dimensional projection map while still preserving the properties of the local neighborhoods of spectra. We find that the majority (178,483) of the 209,533 Galah spectra considered in this study represents normal single stars, whereas 31,050 peculiar and problematic spectra with very diverse spectral features pertaining to 28,579 stars are distributed into 10 classification categories: hot stars, cool metal-poor giants, molecular absorption bands, binary stars, Hμ/Hβ emission, Hμ/Hβ emission superimposed on absorption, Hμ/Hβ P-Cygni, Hμ/Hβ inverted P-Cygni, lithium absorption, and problematic. Classified spectra with supplementary information are presented in the catalog, indicating candidates for follow-up observations and population studies of the short-lived phases of stellar evolution.

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KW - binaries: general

KW - catalogs

KW - methods: data analysis

KW - stars: activity

KW - stars: peculiar

KW - surveys

UR - http://www.scopus.com/inward/record.url?scp=85014831098&partnerID=8YFLogxK

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DO - 10.3847/1538-4365/228/2/24

M3 - Article

VL - 228

JO - The Astrophysical Journal Supplement Series

JF - The Astrophysical Journal Supplement Series

SN - 0067-0049

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ER -