Discovery of an unusual dwarf galaxy in the outskirts of the Milky Way

M. J. Irwin, V. Belokurov, N. W. Evans, E. V. Ryan-Weber, J. T. A. de Jong, S. Koposov, D. B. Zucker, S. T. Hodgkin, G. Gilmore, P. Prema, L. Hebb, A. Begum, M. Fellhauer, P. C. Hewett, R. C. Kennicutt, M. I. Wilkinson, D. M. Bramich, S. Vidrih, H. -W. Rix, T. C. BeersJ. C. Barentine, H. Brewington, M. Harvanek, J. Krzesinski, D. Long, A. Nitta, S. A. Snedden

Research output: Contribution to journalArticlepeer-review

254 Citations (Scopus)

Abstract

We announce the discovery of a new dwarf galaxy, Leo T, in the Local Group. It was found as a stellar overdensity in the Sloan Digital Sky Survey Data Release 5 (SDSS DR5). The color-magnitude diagram of Leo T shows two well-defined features, which we interpret as a red giant branch and a sequence of young, massive stars. As judged from fits to the color-magnitude diagram, it lies at a distance of similar to 420 kpc and has an intermediate-age stellar population with a metallicity of [Fe/H] = - 1.6, together with a young population of blue stars of age similar to 200 Myr. There is a compact cloud of neutral hydrogen with mass similar to 10(5) M-. and radial velocity + 35 km s(-1) coincident with the object visible in the HIPASS channel maps. Leo T is the smallest, lowest luminosity galaxy found to date with recent star formation. It appears to be a transition object similar to, but much lower luminosity than, the Phoenix dwarf.

Original languageEnglish
Number of pages4
JournalAstrophysical Journal Letters
Volume656
Publication statusPublished - 10 Feb 2007

Keywords

  • galaxies : dwarf
  • galaxies : individual (Leo)
  • Local Group
  • DIGITAL SKY SURVEY
  • LOCAL GROUP
  • DATA RELEASE
  • URSA-MAJOR
  • SYSTEM
  • SATELLITE
  • CALIBRATION
  • CAMERA
  • FIELD

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