论文标题
本地组类似物$λ$ CDM宇宙学模拟
Local Group Analogs in $Λ$CDM cosmological simulations
论文作者
论文摘要
我们使用基于两个高分辨率宇宙学$ n $体模拟的半分析星系目录，即Millennium-Wmap7和Millennium-II，以研究本地组（LG）类似物的形成。与以前的研究不同，我们使用观察到的恒星质量选择LG成员（银河系（MW）和M31）类似物，然后使用观察到的两个主要成员星系的分离，分离和运动学对约束施加约束。通过比较MW和M31之间的径向和低纤维化轨道，我们发现更高的切向速度会导致较高的总质量，为4.4 $^{+2.4} _ { - 1.5} \ times $ 10 $^{12} \ rm m _ {\ rm m _ {\ odot} $和6.6 $^{+2.7} _ { - 1.5} \ times $ 10 $^{12} \ rm m _ {\ odot} $用于径向和低纤维化轨道。轨道还会影响MW和M31类似物的个体质量分布。对于径向轨道，MW和M31的典型主机光环质量为1.5 $^{+1.4} _ { - 0.7} \ times $ 10 $^{12} \ rm m _ {\ odot} $ m _ {\ odot} $;对于低纤维化轨道，质量为2.5 $^{+2.2} _ { - 1.4} \ times $ 10 $^{12} \ rm m _ {\ odot} $和3.8 $^{+2.8} _ { - 1.8} _ { - 1.8} \ times $ 10 $^$ 10 $^{12} $ ___ LG主要位于细丝中，尾部向更高的密度延伸至$δ\ sim4.5 $。 MW和M31类似物的暗物质速度各向异性参数$β$在中心接近零，在50--80 kpc时增加到0.2---0.3，并缓慢地向外降低。斜率比从MW卫星计算得的要稍微得多，并且振幅比光晕恒星所追踪的小。来自不同示踪剂的$β$的值在$ \ sim $ 120 kpc的情况下同意$β\ sim $ 0.2。我们还发现，模型预测与MW和M31围绕卫星的径向分布和光度函数的观察至关重要。
We use semi-analytic galaxy catalogs based on two high-resolution cosmological $N$-body simulations, Millennium-WMAP7 and Millennium-II, to investigate the formation of the Local Group (LG) analogs. Unlike previous studies, we use the observed stellar masses to select the LG member (Milky Way (MW) and M31) analogs, and then impose constrains using the observed separation, isolation, and kinematics of the two main member galaxies. By comparing radial and low-ellipticity orbits between the MW and M31, we find higher tangential velocity results in higher total mass, which are 4.4$^{+2.4}_{-1.5}\times$10$^{12}\rm M_{\odot}$ and 6.6$^{+2.7}_{-1.5}\times$10$^{12}\rm M_{\odot}$ for radial and low-ellipticity orbits. The orbits also influence the individual mass distribution of MW and M31 analogs. For radial orbits, the typical host halo masses of the MW and M31 are 1.5$^{+1.4}_{-0.7}\times$10$^{12}\rm M_{\odot}$ and 2.5$^{+1.3}_{-1.1}\times$10$^{12}\rm M_{\odot}$; for low-ellipticity orbits, the masses are 2.5$^{+2.2}_{-1.4}\times$10$^{12}\rm M_{\odot}$ and 3.8$^{+2.8}_{-1.8}\times$10$^{12} \rm M_{\odot}$. The LG is located primarily in filaments with tails extending toward higher densities up to $δ\sim4.5$. The dark matter velocity anisotropy parameters $β$ of both the MW and M31 analogs are close to zero in the center, increasing to 0.2--0.3 at 50--80 kpc and decreasing slowly outward. The slope is much flatter than computed from the MW satellites, and the amplitude is smaller than traced by halo stars. Values of $β$ from different tracers agree at $\sim$120 kpc where $β\sim$ 0.2. We also find that model predictions agree broadly with observations in the radial distribution and luminosity function of satellites around the MW and M31.
