Discovery of a new faint dwarf galaxy associated with NGC 253

D. J. Sand, D. Crnojević, J. Strader, E. Toloba, J. D. Simon, N. Caldwell, P. Guhathakurta, B. McLeod, A. C. Seth

Research output: Contribution to journalArticlepeer-review

54 Scopus citations


We report the discovery of a new faint dwarf galaxy, which we dub Scl-MM-Dw1, at a projected distance of ∼65 kpc from the spiral galaxy NGC 253. The discovery results from the Panoramic Imaging Survey of Centaurus and Sculptor (PISCeS), a program with the Magellan/Megacam imager to study faint substructure in resolved stellar light around massive galaxies outside of the Local Group. We measure a tip of the red giant branch distance to Scl-MM-Dw1 of D = 3.9 ± 0.5 Mpc, consistent with that of NGC 253, making their association likely. The new dwarf's stellar population is complex, with an old, metal-poor red giant branch (≳10 Gyr, [Fe/H] ∼ -2), and an asymptotic giant branch with an age of ∼500 Myr. Scl-MM-Dw1 has a half-light radius of rh = 340 ± 50 pc and an absolute magnitude of MV = -10.3 ± 0.6 mag, comparable to the Milky Way's satellites at the same luminosity. Once complete, our imaging survey of NGC 253 and other nearby massive galaxies will provide a census of faint substructure in halos beyond the Local Group, both to put our own environment into context and to confront models of hierarchical structure formation.

Original languageEnglish (US)
Article numberL7
JournalAstrophysical Journal Letters
Issue number1
StatePublished - Sep 20 2014
Externally publishedYes


  • Dark matter
  • Galaxies: dwarf online-only material: color figures

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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