Structure of the SMC
Stellar component distribution from 2MASS dataI. Gonidakis1, E. Livanou1, E. Kontizas2, U. Klein3, M. Kontizas1, M. Belcheva1, P. Tsalmantza4, and A. Karampelas1
1 Department of Astrophysics Astronomy & Mechanics, Faculty of Physics, University of Athens, 15783 Athens, Greece
2 Institute for Astronomy and Astrophysics, National Observatory of Athens, PO Box 20048, 11810 Athens, Greece
3 Radioastronomisches Institut der Universitat Bonn, Auf dem Hogel 71, 53121 Bonn, Germany
4 Max-Planck-Institut fur Astronomie, Konigstuhl 17, 69117 Heidelberg, Germany
Received 21 March 2008 / Accepted 24 November 2008
Aims. The spatial distribution of the SMC stellar component is investigated from 2MASS data. The morphology of the different age populations is presented. The center of the distribution is calculated and compared with previous estimations. The rotation of the stellar content and possible consequence of the presence of dark matter is discussed.
Methods. The different stellar populations are identified through a CMD diagram of the 2MASS data. Isopleth contour maps are produced in each case, to reveal the spatial distribution. The derived density profiles are discussed.
Results. The older stellar population follows an exponential profile at projected diameters of about 5 kpc (~5°) for the major axis and ~4 kpc for the minor axis, centred at RA: 051, Dec: -73°7' (J2000.0). The centre coordinates are found to be the same for all the different age population maps and are in good accordance with the kinematical centre of the SMC. However they are found to be considerably different to the coordinates of the centre of the gas distribution. The fact that the older population is found in an exponential disk suggests that the stellar content is rotating, a possible consequence of dark matter presence. The strong interactions between the MCs and the MilkyWay might explain the difference in the distributions of the stellar and gas components. The lack of an observed velocity element, which implies an absence of rotation and contradicts the consequences of an exponential profile of the stellar component, may also be a result of gravitational interactions.
Key words: galaxies: Magellanic Clouds -- galaxies: structure -- cosmology: dark matter
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