TY - JOUR

T1 - A wide-field view of Leo II

T2 - a structural analysis using the Sloan Digital Sky Survey

AU - Coleman, Matthew G.

AU - Jordi, Katrin

AU - Rix, Hans-Walter

AU - Grebel, Eva K.

AU - Koch, Andreas

PY - 2007/10/1

Y1 - 2007/10/1

N2 - 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.

AB - 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.

U2 - 10.1086/522229

DO - 10.1086/522229

M3 - Journal article

VL - 134

SP - 1938

EP - 1951

JO - The Astronomical Journal

JF - The Astronomical Journal

SN - 0004-6256

IS - 5

ER -