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Kinematic subpopulations in dwarf spheroidal galaxies

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  • Uğur Ural
  • Mark I. Wilkinson
  • Andreas Koch
  • Gerard Gilmore
  • Timothy C. Beers
  • V. Belokurov
  • N. Wyn Evans
  • E.K. Grebel
  • Simon Vidrih
  • D. B. Zucker
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<mark>Journal publication date</mark>18/12/2009
<mark>Journal</mark>Monthly Notices of the Royal Astronomical Society
Issue number2
Volume402
Number of pages12
Pages (from-to)1357-1368
Publication StatusPublished
<mark>Original language</mark>English

Abstract

We present new spectroscopic data for 26 stars in the recently discovered Canes Venatici I (CVn I) dwarf spheroidal galaxy, obtained with the Gemini Multi-Object Spectrograph North (GMOS-N) on the Gemini North telescope. We use these data to investigate the recent claim of the presence of two dynamically inconsistent stellar populations in this system. While we find no evidence for kinematically distinct subpopulations in our sample, we also show that the available kinematic data set in CVnI is likely too small to draw robust conclusions about its subpopulations. We are, however, able to obtain a mass estimate for CVn I that is consistent with all available data, including previously published data. We discuss possible differences between our sample and the earlier data set, and study the general detectability of subpopulations in small kinematic samples. We conclude that, in the absence of additional supporting observational evidence (e.g. metallicity gradients), subpopulations in small kinematic samples (typically fewer than 100 stars) should be treated with caution, as their identification depends on multiple parameters and rarely produces a signal at a high confidence level. It is therefore essential to explicitly determine the statistical significance of any suggested subpopulation.