MAGELLAN/M2FS SPECTROSCOPY of TUCANA 2 and GRUS 1

Matthew G. Walker, Mario Mateo, Edward W. Olszewski, Sergey Koposov, Vasily Belokurov, Prashin Jethwa, David L. Nidever, Vincent Bonnivard, John I.Bailey Iii, Eric F. Bell, Sarah R. Loebman

Research output: Contribution to journalArticle

49 Scopus citations

Abstract

We present results from spectroscopic observations with the Michigan/Magellan Fiber System (M2FS) of 147 stellar targets along the line of sight to the newly discovered "ultrafaint" stellar systems Tucana 2 (Tuc 2) and Grus 1 (Gru 1). Based on simultaneous estimates of line of sight velocity and stellar-atmospheric parameters, we identify 8 and 7 stars as probable members of Tuc 2 and and Gru 1, respectively. Our sample for Tuc 2 is sufficient to resolve an internal velocity dispersion of km s-1 about a mean of km s-1 (solar rest frame), and to estimate a mean metallicity of [Fe/H] =. These results place Tuc 2 on chemodynamical scaling relations followed by dwarf galaxies, suggesting a dominant dark matter component with dynamical mass enclosed within the central ∼160 pc, and dynamical mass-to-light ratio . For Gru 1 we estimate a mean velocity of km s-1 and a mean metallicity of [Fe/H] = but our sample does not resolve Gru 1's velocity dispersion. The radial coordinates of Tuc 2 and Gru 1 in Galactic phase space suggest that their orbits are among the most energetic within a distance of . Moreover, their proximity to each other in this space arises naturally if both objects are trailing the Large Magellanic Cloud.

Original languageEnglish (US)
Article number53
JournalAstrophysical Journal
Volume819
Issue number1
DOIs
StatePublished - Mar 1 2016

Keywords

  • Local Group
  • galaxies: dwarf
  • galaxies: individual (Tucana 2, Gru 1)
  • galaxies: kinematics and dynamics
  • techniques: spectroscopic

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Walker, M. G., Mateo, M., Olszewski, E. W., Koposov, S., Belokurov, V., Jethwa, P., Nidever, D. L., Bonnivard, V., Iii, J. I. B., Bell, E. F., & Loebman, S. R. (2016). MAGELLAN/M2FS SPECTROSCOPY of TUCANA 2 and GRUS 1. Astrophysical Journal, 819(1), [53]. https://doi.org/10.3847/0004-637X/819/1/53