Open AccessKinematic subpopulations in dwarf spheroidal galaxies
Author(s) -
Ural Uğur,
Wilkinson Mark I.,
Koch Andreas,
Gilmore Gerard,
Beers Timothy C.,
Belokurov Vasily,
Evans N. Wyn,
Grebel Eva K.,
Vidrih Simon,
Zucker Daniel B.
Publication year - 2010
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2009.15975.x
Subject(s) - physics , kinematics , astrophysics , dwarf galaxy , stars , galaxy , metallicity , stellar kinematics , astronomy , data set , milky way , statistics , classical mechanics , mathematics
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.