A wide-field view of Leo II:a structural analysis using the Sloan Digital Sky Survey

Coleman, Matthew G. and Jordi, Katrin and Rix, Hans-Walter and Grebel, Eva K. and Koch, Andreas (2007) A wide-field view of Leo II:a structural analysis using the Sloan Digital Sky Survey. The Astronomical Journal, 134 (5). pp. 1938-1951. ISSN 0004-6256

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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 4 × 4 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 rc = 2.64' ± 0.19' (178 ± 13 pc), a tidal radius of rt = 9.33' ± 0.47' (632 ± 32 pc), and a total V-band luminosity of LV = (7.4 ± 2.0) × 105 L⊙ (MV = -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.

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Journal Article
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The Astronomical Journal
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05 Dec 2016 14:06
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18 Nov 2020 12:45