Tidal signatures in the faintest milky way satellites: The detailed properties of Leo V, Pisces II, and Canes Venatici II

David J. Sand, Jay Strader, Beth Willman, Dennis Zaritsky, Brian McLeod, Nelson Caldwell, Anil Seth, Edward Olszewski

Research output: Contribution to journalArticle

65 Scopus citations

Abstract

We present deep wide-field photometry of three recently discovered faint Milky Way (MW) satellites: LeoV, PiscesII, and Canes Venatici II. Our main goals are to study the structure and star formation history of these dwarfs; we also search for signs of tidal disturbance. The three satellites have similar half-light radii (∼60-90 pc) but a wide range of ellipticities. Both LeoV and CVnII show hints of stream-like overdensities at large radii. An analysis of the satellite color-magnitude diagrams shows that all three objects are old (>10Gyr) and metal-poor ([Fe/H] ∼-2), though neither the models nor the data have sufficient precision to assess when the satellites formed with respect to cosmic reionization. The lack of an observed younger stellar population (≲ 10Gyr) possibly sets them apart from the other satellites at Galactocentric distances ≳ 150kpc. We present a new compilation of structural data for all MW satellite galaxies and use it to compare the properties of classical dwarfs to the ultra-faints. The ellipticity distribution of the two groups is consistent at the ∼2σ level. However, the faintest satellites tend to be more aligned toward the Galactic Center, and those satellites with the highest ellipticity (≳ 0.4) have orientations (ΔθGC) in the range 20° ≲ Δθ GC ≲ 40°. This latter observation is in rough agreement with predictions from simulations of dwarf galaxies that have lost a significant fraction of their dark matter halos and are being tidally stripped.

Original languageEnglish (US)
Article number79
JournalAstrophysical Journal
Volume756
Issue number1
DOIs
StatePublished - Jan 1 2012

Keywords

  • Local Group
  • galaxies: dwarf

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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