2007AJ....134.1938C

Using SDSS I data, we have analyzed the stellar distribution of the Leo II dwarf spheroidal galaxy (distance of 233 kpc) to search for evidence of tidal deformation. The existing SDSS photometric catalog contains gaps in regions of high stellar crowding, hence we filled the area at the center of Leo II using the DAOPHOT algorithm applied to the SDSS images. The combined DAOPHOT-SDSS data set contains three-filter photometry over a 4x4 deg² region centered on Leo II. By defining a mask in three-filter color-magnitude space, we removed the majority of foreground field stars. We have measured the following Leo II structural parameters: a core radius of r_c=2.64'±0.19' (178±13 pc), a tidal radius of r_t=9.33'±0.47' (632±32 pc), and a total V-band luminosity of L_V=(7.4±2.0)x10⁵ L_☉(M_V=-9.9±0.3). Our comprehensive analysis of the Leo II structure did not reveal any significant signs of tidal distortion. The internal structure of this object contains only mild isophotal twisting. A small overdensity was discovered approximately 4.5 tidal radii from the Leo II center; however, we conclude that it is unlikely to be material tidally stripped from Leo II based on its stellar population and is most likely a foreground overdensity of stars. Our results indicate that the influence of the Galactic gravitational field on the structure of Leo II has been relatively mild. We rederived the mass-to-light ratio of this system using existing kinematic data combined with our improved structural measurements, and we favor the scenario in which Leo II is strongly dominated by dark matter with (M/L)_V∼100 in solar units.