Volume 570, October 2014
|Number of page(s)||11|
|Published online||21 October 2014|
1 European Southern Observatory, Alonso de Cordova 3107, Vitacura Santiago, Chile
2 INAF – Osservatorio Astronomico di Bologna, Via Ranzani 1, 40127 Bologna, Italy
3 Dipartimento di Astronomia - Università degli Studi di Bologna, Via Ranzani 1, 40127 Bologna, Italy
4 Department of Astronomy and Astrophysics, Pontificia Universidad Católica de Chile, Avenida Vicuña Mackenna 4860, Macul, Santiago, Chile
5 Netherlands Institute for Radio Astronomy, Postbus 2, 7990 AA Dwingeloo, The Netherlands
6 Kapteyn Astronomical Institute, University of Groningen, Postbus 800, 9700 AV Groningen, The Netherlands
7 INAF – Osservatorio Astronomico di Roma, via Frascati 33, 00040 Monteporzio, Italy
8 Instituto de Astrofsica de Canarias, 38205 La Laguna, Tenerife, Spain
Received: 16 June 2014
Accepted: 6 August 2014
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).
Key words: galaxies: dwarf / Local Group / galaxies: ISM
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 cdsarc.u-strasbg.fr (188.8.131.52) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/570/A78
© ESO, 2014
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