The VISTA near infrared survey of the Magellanic System (VMC) will provide deep YJKs photometry reaching stars in the oldest turn-off point all over the Magellanic Clouds (MCs). As part of the preparation for the survey, we aim to access the accuracy in the Star Formation History (SFH) that can be expected from VMC data, in particular for the LMC. To this aim, we first simulate VMC images containing not only the LMC stellar populations but also the foreground MW stars and background galaxies. We perform aperture photometry over these simulated images, access the expected levels of photometric errors and incompleteness, and apply the classical technique of SFH-recovery based on the reconstruction of colour-magnitude diagrams (CMD) via the minimization of a chi-squared-like statistics. We then evaluate the expected errors in the recovered star formation rate as a function of stellar age, SFR(t), starting from models with a known Age--Metallicity Relation (AMR). It turns out that, for a given sky area, the random errors for ages older than ~0.4 Gyr seem to be independent of the crowding. For a spatial resolution of ~0.1 sqdeg, the random errors in SFR(t) will be below 20% for this wide range of ages. On the other hand, due to the smaller stellar statistics for stars younger than ~0.4 Gyr, the outer LMC regions will require larger areas to achieve the same level of accuracy in the SFR(t). If we consider the AMR as unknown, the SFH-recovery algorithm is able to accurately recover the input AMR, at the price of an increase of random errors in the SFR(t) by a factor of about 2.5. Experiments of SFH-recovery performed for varying distance modulus and reddening indicate that the propagation of the errors in these parameters in the SFR(t) implies systematic errors below 30%.
Dynamics of the Magellanic Clouds in a LCDM Universe
我们研究银河系麦哲伦云系统选择千禧年-II模拟，以放置在宇宙学背景下的麦哲伦云的轨道。我们的分析表明，卫星质量足够大的LMC类似物通常是在后期吸积。此外，那些在早期吸积并存活到现在的轨道特性与大麦哲伦星系观测到的轨道特性不一致。大麦哲伦星系的高速度，加上模拟中看到的未束缚轨道的缺乏，表明MW的晕的质量不太可能小于2 x 10^12 Msun。这一结论进一步支持统计的晕托管卫星的质量，速度和分离的LMC。我们进一步表明：（1）在MW质量晕中，LMC和SMC质量的天体并不特别罕见;（2）LMC明显的高角动量在宇宙学上并不罕见;（3）在z=0时，MW晕中很少有LMC-SMC双星系统，但在较晚的时候，高速双星对是可能的。基于这些结果，我们得出结论，LMC吸积在过去的四个Gyr，目前正在进行其第一次pericentric通过MW。
Search for Gamma-ray Emission from Dark Matter Annihilation in the Large Magellanic Cloud with the Fermi Large Area Telescope
在50千秒差距的距离和$\sim10^{10}$ M $_{\odot}$的暗物质质量，大麦云云（LMC）是间接暗物质搜索的天然目标。我们使用五年的数据从费米大面积望远镜（LAT）和更新的模型的伽马射线发射的标准天体物理组件，以寻找一个暗物质湮灭信号从大麦哲伦星云。我们进行旋转曲线分析，以确定暗物质的分布，设置一个强大的最小暗物质的量在LMC，我们用它来设置保守的界限上的湮灭截面。LMC的辐射通常可以用标准天体物理源很好地描述，一旦考虑到系统的不确定性，在LMC的运动中心附近最多可以识别出一个$1-2σ$过量。我们把竞争边界上的暗物质湮灭截面作为暗物质粒子质量和湮灭通道的函数。
