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

doi:10.1088/2041-8205/793/1/L7

paper

Discovery of a new faint dwarf galaxy associated with NGC 253

arXiv:1406.6687 · doi:10.1088/2041-8205/793/1/L7

Abstract

We report the discovery of a new faint dwarf galaxy, which we dub Scl-MM-Dw1, at a projected distance of $\sim$ 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 $\pm$ 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] $\sim$ $-$ 2), and an asymptotic giant branch with an age of $\sim$ 500 Myr. Scl-MM-Dw1 has a half-light radius of $r_{h}$ =340 $\pm$ 50 pc and an absolute magnitude of $M_{V}$ = $-$ 10.3 $\pm$ 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.

8 pages, 4 figures, ApJL submitted

Discovery of a new faint dwarf galaxy associated with NGC 253

Abstract

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