A tidally disrupting dwarf galaxy in the halo of NGC 253
- Physics Department, Texas Tech University, Box 41051, Lubbock, TX 79409-1051 (United States)
- Department of Physics, Royal Military College of Canada, P.O. Box 17000, Station Forces, Kingston, ON K7L 7B4 (Canada)
- Carnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)
- UCO/Lick Observatory, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 (United States)
- Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States)
- Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States)
We report the discovery of Scl-MM-Dw2, a new dwarf galaxy at a projected separation of ∼50 kpc from NGC 253, as part of the Panoramic Imaging Survey of Centaurus and Sculptor project (PISCeS). We measure a tip of the red giant branch (RGB) distance of 3.12 ± 0.30 Mpc, suggesting that Scl-MM-Dw2 is likely a satellite of NGC 253. We qualitatively compare the distribution of RGB stars in the color–magnitude diagram with theoretical isochrones and find that it is consistent with an old, ∼12 Gyr, and metal-poor, −2.3 < [Fe/H] < −1.1, stellar population. We also detect a small number of asymptotic giant branch stars consistent with a metal-poor 2–3 Gyr population in the center of the dwarf. Our non-detection of HI in a deep Green Bank Telescope spectrum implies a gas fraction M{sub HI}/L{sub V}<0.02 M{sub ⊙}/L{sub ⊙}. The stellar and gaseous properties of Scl-MM-Dw2 suggest that it is a dwarf spheroidal galaxy. Scl-MM-Dw2 has a luminosity of M{sub V}=−12.1±0.5 mag and a half-light radius of r{sub h} =2.94±0.46 kpc, which makes it moderately larger than dwarf galaxies in the Local Group of the same luminosity. However, Scl-MM-Dw2 is very elongated (ϵ=0.66±0.06), and it has an extremely low surface brightness (μ{sub 0,V}=27.7±0.6 mag arcsec{sup −2}). Its elongation and diffuseness make it an outlier in the ellipticity–luminosity and surface brightness–luminosity scaling relations. These properties suggest that this dwarf is being tidally disrupted by NGC 253.
- OSTI ID:
- 22868730
- Journal Information:
- Astrophysical Journal Letters, Vol. 816, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
Similar Records
DISCOVERY OF A CLOSE PAIR OF FAINT DWARF GALAXIES IN THE HALO OF CENTAURUS A
SHAKEN, NOT STIRRED: THE DISRUPTED DISK OF THE STARBURST GALAXY NGC 253