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The GALAH survey and Gaia DR2 : (non-)existence of five sparse high-latitude open clusters

Kos, Janez; de Silva, Gayandhi; Buder, Sven; Bland-Hawthorn, Joss; Sharma, Sanjib; Asplund, Martin; D'Orazi, Valentina; Duong, Ly; Freeman, Ken and Lewis, Geraint F., et al. (2018) In Monthly Notices of the Royal Astronomical Society 480(4). p.5242-5259
Abstract

Sparse open clusters can be found at high galactic latitudes where loosely populated clusters are more easily detected against the lower stellar background. Because most star formation takes place in the thin disc, the observed population of clusters far from the Galactic plane is hard to explain. We combined spectral parameters from the GALAH survey with the Gaia DR2 catalogue to study the dynamics and chemistry of five old sparse high-latitude clusters in more detail. We find that four of them (NGC 1252, NGC 6994, NGC 7772, NGC 7826) - originally classified in 1888-are not clusters but are instead chance projections on the sky. Member stars quoted in the literature for these four clusters are unrelated in our multidimensional physical... (More)

Sparse open clusters can be found at high galactic latitudes where loosely populated clusters are more easily detected against the lower stellar background. Because most star formation takes place in the thin disc, the observed population of clusters far from the Galactic plane is hard to explain. We combined spectral parameters from the GALAH survey with the Gaia DR2 catalogue to study the dynamics and chemistry of five old sparse high-latitude clusters in more detail. We find that four of them (NGC 1252, NGC 6994, NGC 7772, NGC 7826) - originally classified in 1888-are not clusters but are instead chance projections on the sky. Member stars quoted in the literature for these four clusters are unrelated in our multidimensional physical parameter space; the quoted cluster properties in the literature are therefore meaningless. We confirm the existence of visually similar NGC 1901 for which we provide a probabilistic membership analysis. An overdensity in three spatial dimensions proves to be enough to reliably detect sparse clusters, but the whole six-dimensional space must be used to identify members with high confidence, as demonstrated in the case of NGC 1901.

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subject
keywords
Catalogues, Parallaxes, Proper motions, Surveys, Techniques: radial velocities
in
Monthly Notices of the Royal Astronomical Society
volume
480
issue
4
pages
18 pages
publisher
Oxford University Press (OUP)
external identifiers
  • scopus:85055208730
ISSN
0035-8711
DOI
10.1093/MNRAS/STY2171
language
English
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no
id
44f84355-193c-4342-97b7-43acc4c83c4c
date added to LUP
2019-05-29 19:40:28
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2019-09-15 05:18:34
@article{44f84355-193c-4342-97b7-43acc4c83c4c,
  abstract     = {<p>Sparse open clusters can be found at high galactic latitudes where loosely populated clusters are more easily detected against the lower stellar background. Because most star formation takes place in the thin disc, the observed population of clusters far from the Galactic plane is hard to explain. We combined spectral parameters from the GALAH survey with the Gaia DR2 catalogue to study the dynamics and chemistry of five old sparse high-latitude clusters in more detail. We find that four of them (NGC 1252, NGC 6994, NGC 7772, NGC 7826) - originally classified in 1888-are not clusters but are instead chance projections on the sky. Member stars quoted in the literature for these four clusters are unrelated in our multidimensional physical parameter space; the quoted cluster properties in the literature are therefore meaningless. We confirm the existence of visually similar NGC 1901 for which we provide a probabilistic membership analysis. An overdensity in three spatial dimensions proves to be enough to reliably detect sparse clusters, but the whole six-dimensional space must be used to identify members with high confidence, as demonstrated in the case of NGC 1901.</p>},
  author       = {Kos, Janez and de Silva, Gayandhi and Buder, Sven and Bland-Hawthorn, Joss and Sharma, Sanjib and Asplund, Martin and D'Orazi, Valentina and Duong, Ly and Freeman, Ken and Lewis, Geraint F. and Lin, Jane and Lind, Karin and Martell, Sarah L. and Schlesinger, Katharine J. and Simpson, Jeffrey D. and Zucker, Daniel B. and Zwitter, Tomaž and Bedding, Timothy R. and Čotar, Klemen and Horner, Jonathan and Nordlander, Thomas and Stello, Denis and Ting, Yuan Sen and Traven, Gregor},
  issn         = {0035-8711},
  keyword      = {Catalogues,Parallaxes,Proper motions,Surveys,Techniques: radial velocities},
  language     = {eng},
  month        = {01},
  number       = {4},
  pages        = {5242--5259},
  publisher    = {Oxford University Press (OUP)},
  series       = {Monthly Notices of the Royal Astronomical Society},
  title        = {The GALAH survey and Gaia DR2 : (non-)existence of five sparse high-latitude open clusters},
  url          = {http://dx.doi.org/10.1093/MNRAS/STY2171},
  volume       = {480},
  year         = {2018},
}