Based on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada–France–Hawaii Telescope (CFHT) which is operated by the National Research Council (NRC) of Canada, the Institute National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii. Also based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Institute. STScI is operated by the association of Universities for Research in Astronomy, Inc. under the NASA contract NAS 5-26555.
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Draco, a flawless dwarf galaxy†
Article first published online: 24 JAN 2007
DOI: 10.1111/j.1365-2966.2006.11356.x
Issue
Monthly Notices of the Royal Astronomical Society
Volume 375, Issue 3, pages 831–842, March 2007
Additional Information
How to Cite
Ségall, M., Ibata, R. A., Irwin, M. J., Martin, N. F. and Chapman, S. (2007), Draco, a flawless dwarf galaxy. Monthly Notices of the Royal Astronomical Society, 375: 831–842. doi: 10.1111/j.1365-2966.2006.11356.x
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Publication History
- Issue published online: 30 JAN 2007
- Article first published online: 24 JAN 2007
- Accepted 2006 November 29. Received 2006 November 28; in original form 2006 November 2
Keywords:
- galaxies: dwarf;
- galaxies: structure;
- dark matter
ABSTRACT
The Draco dwarf spheroidal galaxy (dSph), with its apparent immense mass-to-light ratio and compact size, holds many clues to the nature of the enigmatic dark matter. Here we present deep photometric studies of this dwarf galaxy, undertaken with the MegaCam Camera at the Canada–France–Hawaii Telescope, the Wide Field Camera at the Isaac Newton Telescope and the Wide Field and Planetary Camera onboard the Hubble Space Telescope (HST). The new photometric data cover the entirety of the galaxy, and reach i′= 24.5 at 50 per cent completeness, significantly deeper than previous panoramic studies, allowing searches for tidal disturbances of much lower surface brightness than has been possible before. With these improved statistics, we find no evidence for asymmetric disturbances or tidal tails that possess more than 3 per cent of the stars found within the centre of the galaxy. We find that the central stellar density, as probed by the HST data, rises into the central 0.5 arcmin. Uncertainties in the position of the centroid of the galaxy do not allow us to determine whether the apparent flattening of the profile interior to 0.5 arcmin is reliable or not. Draco is therefore a flawless dwarf galaxy, featureless and apparently unaffected by Galactic tides.