The extended structure of the dwarf irregular galaxy Sagittarius

G. Beccari, M. Bellazzini, F. Fraternali, G. Battaglia, S. Perina, A. Sollima, T. A. Oosterloo, V. Testa, S. Galleti

Research output: Contribution to journalArticleAcademicpeer-review

9 Citations (Scopus)
182 Downloads (Pure)


We present a detailed study of the stellar and H i structure of the dwarf irregular galaxy Sagittarius. We use new deep and wide field photometry to trace the surface brightness profile of the galaxy out to ≃5.0' (corresponding to ≃1600 pc) and down to μV ≃ 30.0 mag/arcsec2, thus showing that the stellar body of the galaxy is much more extended than previously believed, and it is similarly (or more) extended than the overall H i distribution. The whole major-axis profile is consistent with a pure exponential, with a scale radius of ≃340 pc. The surface density maps reveal that the distribution of old and intermediate-age stars is smooth and remarkably flattened out to its edges, while the associated H i has a much rounder shape, is off-centred and presents multiple density maxima and a significant hole. No clear sign of systemic rotation is detectable in the complex H i velocity field. No metallicity gradient is detected in the old and intermediate age population of the galaxy, and we confirm that this population has a much more extended distribution than young stars (age ≲ 1 Gyr). Based on data obtained with the European Southern Observatory Very Large Telescope, Paranal, Chile, under the Program 089.D-0052(A).Table of stellar photometry (IN6) is only available at the CDS via anonymous ftp to ( or via
Original languageEnglish
Article numberA78
Number of pages11
JournalAstronomy and astrophysics
Publication statusPublished - Oct-2014


  • galaxies: dwarf
  • Local Group
  • galaxies: ISM
  • Deep VI photometry of Sgr dIrr

    Beccari, G. (Contributor), Bellazzini, M. (Contributor), Fraternali, F. (Contributor), Battaglia, G. (Contributor), Perina, S. (Contributor), Sollima, A. (Contributor), Oosterloo, T. (Contributor), Testa, V. (Contributor) & Galleti, S. (Contributor), University of Groningen, 21-Oct-2014


Cite this