The discovery of Segue 2: A prototype of the population of satellites of satellites

V. Belokurov, M. G. Walker, N. W. Evans, G. Gilmore, M. J. Irwin, M. Mateo, L. Mayer, Edward W Olszewski, Jill Bechtold, T. Pickering

Research output: Contribution to journalArticle

135 Citations (Scopus)

Abstract

We announce the discovery of a new Milky Way satellite Segue 2 found in the data of the Sloan Extension for Galactic Understanding and Exploration (SEGUE). We followed this up with deeper imaging and spectroscopy on the Multiple Mirror Telescope (MMT). From this, we derive a luminosity of Mv = -2.5, a half-light radius of 34 pc and a systemic velocity of ∼ -40 km s-1. Our data also provide evidence for a stream around Segue 2 at a similar heliocentric velocity, and the SEGUE data show that it is also present in neighbouring fields. We resolve the velocity dispersion of Segue 2 as 3.4 km s-1 and the possible stream as ∼7 km s-1. This object shows points of comparison with other recent discoveries, Segue 1, Boo II and Coma. We speculate that all four objects may be representatives of a population of satellites of satellites - survivors of accretion events that destroyed their larger but less dense parents. They are likely to have formed at redshifts z > 10 and are good candidates for fossils of the reionization epoch.

Original languageEnglish (US)
Pages (from-to)1748-1755
Number of pages8
JournalMonthly Notices of the Royal Astronomical Society
Volume397
Issue number4
DOIs
StatePublished - Aug 2009

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prototypes
coma
fossils
spectroscopy
accretion
luminosity
time measurement
telescopes
fossil
mirrors
radii
comparison

Keywords

  • Galaxies: dwarf
  • Galaxies: individual: Segue 2
  • Local Group

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Belokurov, V., Walker, M. G., Evans, N. W., Gilmore, G., Irwin, M. J., Mateo, M., ... Pickering, T. (2009). The discovery of Segue 2: A prototype of the population of satellites of satellites. Monthly Notices of the Royal Astronomical Society, 397(4), 1748-1755. https://doi.org/10.1111/j.1365-2966.2009.15106.x

The discovery of Segue 2 : A prototype of the population of satellites of satellites. / Belokurov, V.; Walker, M. G.; Evans, N. W.; Gilmore, G.; Irwin, M. J.; Mateo, M.; Mayer, L.; Olszewski, Edward W; Bechtold, Jill; Pickering, T.

In: Monthly Notices of the Royal Astronomical Society, Vol. 397, No. 4, 08.2009, p. 1748-1755.

Research output: Contribution to journalArticle

Belokurov, V. ; Walker, M. G. ; Evans, N. W. ; Gilmore, G. ; Irwin, M. J. ; Mateo, M. ; Mayer, L. ; Olszewski, Edward W ; Bechtold, Jill ; Pickering, T. / The discovery of Segue 2 : A prototype of the population of satellites of satellites. In: Monthly Notices of the Royal Astronomical Society. 2009 ; Vol. 397, No. 4. pp. 1748-1755.
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