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Abstract: Using SDSS I data, we have analysed the stellar distribution of the Leo IIdwarf spheroidal galaxy distance of 233 kpc to search for evidence of tidaldeformation. The existing SDSS photometric catalogue contains gaps in regionsof high stellar crowding, hence we filled the area at the centre of Leo IIusing the DAOPHOT algorithm applied to the SDSS images. The combinedDAOPHOT-SDSS dataset contains three-filter photometry over a 4x4 square degreeregion centred on Leo II. By defining a mask in three-filter colour-magnitudespace, we removed the majority of foreground field stars. We have measured thefollowing Leo II structural parameters: a core radius of r c = 2.64 +- 0.19arcmin 178 +- 13 pc, a tidal radius of r t = 9.33 +- 0.47 arcmin 632 +-32 pc and a total V-band luminosity of L V = 7.4 +- 2.0 times 10^5 L sunM V = -9.9 +- 0.3. Our comprehensive analysis of the Leo II structure didnot reveal any significant signs of tidal distortion. The internal structure ofthis object contains only mild isophotal twisting. A small overdensity wasdiscovered appoximately 4.5 tidal radii from the Leo II centre, however weconclude it is unlikely to be material tidally stripped from Leo II based onits stellar population, and is most likely a foreground overdensity of stars.Our results indicate that the influence of the Galactic graviational field onthe structure of Leo II has been relatively mild. We rederived themass-to-light ratio of this system using existing kinematic data combined withour improved structural measurements, and favour the scenario in which Leo IIis strongly dominated by dark matter with M-L V ~ 100 in solar units.



Autor: Matthew G. Coleman 1, Katrin Jordi 2, Hans-Walter Rix 1, Eva K. Grebel 2, Andreas Koch 3 1 Max-Planck-Institut fur Astronomie, He

Fuente: https://arxiv.org/







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