An optical and H i study of the dwarf Local Group galaxy VV124 = UGC4879: A gas-poor dwarf with a stellar disk?

M. Bellazzini*, G. Beccari, T. A. Oosterloo, S. Galleti, A. Sollima, M. Correnti, V. Testa, L. Mayer, M. Cignoni, F. Fraternali, S. Gallozzi

*Corresponding author for this work

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Abstract

We present a detailed study of the dwarf galaxy VV124 (UGC4879), recently recognized as a remarkably isolated member of the Local Group. We have obtained deep (r' 26:5) wide-field (230 230) g,r photometry of individual stars with the LBC camera at the Large Binocular Telescope under sub-arcsec seeing conditions,. The Color-Magnitude Diagram suggests that the stellar content of the galaxy is dominated by an old, metal-poor population, with a significant metallicity spread. A very clean detection of the RGB tip allows us to derive an accurate distance of D = 1:3 0:1 Mpc. Combining surface photometry with star counts, we are able to trace the surface brightness profile of VV124 out to 50 ' 1:9 kpc radius (where r ' 30 mag/arcsec2), showing that it is much more extended than previously believed. Moreover, the surface density map reveals the presence of two symmetric flattened wings emanating from the central elongated spheroid and aligned with its major axis, resembling a stellar disk seen nearly edge-on. We also present Hi observations obtained with the Westerbork Synthesis Radio Telescope (WSRT), the first ever of this object. A total amount of ' 106 M of Hi gas is detected in VV124. Compared to the total luminosity, this gives a value of MHI=LV = 0:11, which is particularly low for isolated Local Group dwarfs. The spatial distribution of the gas does not correlate with the observed stellar wings. The systemic velocity of the Hi in the region superposed to the stellar main body of the galaxy is Vh =
Original languageEnglish
Article numberA58
Number of pages19
JournalAstronomy & astrophysics
Volume527
DOIs
Publication statusPublished - Mar-2011

Keywords

  • galaxies: dwarf
  • Local Group
  • galaxies: structure
  • galaxies: stellar content
  • galaxies: ISM
  • galaxies: individual: UGC4879
  • DIGITAL SKY SURVEY
  • RED GIANT BRANCH
  • NEUTRAL INTERSTELLAR-MEDIUM
  • GALACTIC GLOBULAR-CLUSTERS
  • SPHEROIDAL GALAXIES
  • STAR-FORMATION
  • MILKY-WAY
  • METALLICITY DISTRIBUTION
  • STRUCTURAL-PROPERTIES
  • CHEMICAL ABUNDANCES

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