The structural properties and star formation history of Leo T from deep LBT photometry
J. T. A. de Jong, J. Harris, M. G. Coleman, N. F. Martin, E. F. Bell, H-W. Rix, J. M. Hill, E. D. Skillman, D. J. Sand, E. W. Olszewski, D. Zaritsky, D. Thompso… 展开作者
J. T. A. de Jong, J. Harris, M. G. Coleman, N. F. Martin, E. F. Bell, H-W. Rix, J. M. Hill, E. D. Skillman, D. J. Sand, E. W. Olszewski, D. Zaritsky, D. Thompson, E. Giallongo, R. Ragazzoni, A. DiPaola, J. Farinato, V. Testa, J. Bechtold
备注：
8 pages, 9 figures, some small textual changes, accepted for publication in the Astrophysical Journal
We present deep, wide-field g and r photometry of the transition type dwarf galaxy Leo T, obtained with the blue arm of the Large Binocular Telescope. The data confirm the presence of both very young (<1 Gyr) as well as much older (>5 Gyr) stars. We study the structural properties of the old and young stellar populations by preferentially selecting either population based on their color and magnitude. The young population is significantly more concentrated than the old population, with half-light radii of 104+-8 and 148+-16 pc respectively, and their centers are slightly offset. Approximately 10% of the total stellar mass is estimated to be represented by the young stellar population. Comparison of the color-magnitude diagram (CMD) with theoretical isochrones as well as numerical CMD-fitting suggest that star formation began over 10 Gyr ago and continued in recent times until at least a few hundred Myr ago. The CMD-fitting results are indicative of two distinct star formation bursts, with a quiescent period around 3 Gyr ago, albeit at low significance. The results are consistent with no metallicity evolution and [Fe/H] ~ -1.5 over the entire age of the system. Finally, the data show little if any sign of tidal distortion of Leo T.
Exploring Halo Substructure with Giant Stars X. Extended Dark Matter or Tidal Disruption?: The Case for the Leo I Dwarf Spheroidal Galaxy
我们对狮子座I矮球状（dSph）星系进行了宽视场（4.5度^2）的光度和光谱观测，以探索其扩展的形态和动力学。与本系列以前的文章一样，我们利用M、T_2和DDO 51滤波系统中的测光来选择Leo I红巨星分支候选星，到目前为止，这种选择技术已被证明100%可靠地从100多个M < 21.5 Leo I giant candidates having previous or new Keck DEIMOS spectroscopy to a radius >1.3倍于拟合的中心King轮廓的极限半径中选择实际的Leo I成员。所有相似选择的狮子座I巨星候选者的二维分布很好地拟合了一个中心的单分量国王轮廓的极限半径13.3弧分，但许多巨星被发现在这个新推导的国王极限半径之外。因此，密度剖面显示出在长轴径向距离约为10弧分处的断裂，这是由超过国王极限半径的恒星（光谱证实是真正的狮子座I成员）产生的，主要沿着相当细长的卫星主体的长轴。这种空间结构，一个相当平坦的速度色散剖面和狮子座I成员在大半径处的不对称径向速度（RV）分布，共同支持了狮子座I在至少一个，但最多两个，大质量本星系群成员的近银河通道上被潮汐破坏的图片。（节略）
