论文标题
使用Ogle-iv $δ$ Scuti星的银河系凸起的三维结构的MCMC方法
An MCMC Approach to the Three-dimensional Structure of the Milky Way Bulge using OGLE-IV $δ$ Scuti Stars
论文作者
论文摘要
我们对银河膨胀区（$ -8^{\ circ} .3 <l <9^{\ 9^{\ circ} .4 $）的高纬度$Δ$ scuti星星（$ \ weft | b \ right | b \ right |> 1^{\ circ} $）进行了分析。凸起的几何参数是根据五维参数空间中的最大似然（ML）分析确定的。这些参数的更精致值及其不确定性是从完全贝叶斯马尔可夫链蒙特卡洛（MCMC）分析中获得的。将凸起近似为椭圆形，恒星的数量密度分布是以Galacto为中心距离的函数的分布，已使用三个分布函数进行建模：两个指数（$ \ rm E_ {1}，\ rm E_ {2} $）类型和一个高斯（$ \ \ rm g $）类型。基于AIC和BIC值，选择指数模型$ \ rm E_ {1} $作为从MCMC分析获得的参数值的最佳统计模型。 MCMC分析得出以下结果：发现与银河系中心（GC）的平均距离为$ r_ {0} = 8.034 \ pM0.012 _ {\ rm Stat} \ pm0.586 _ {\ rm sys} $ kpc; Bulge $δ$ Scuti分布具有归一化（$ a \ equiv1 $）轴比（$ a：b：c $）的三轴形状，为$ 1.000 \ pm 0.005：0.348 \ pm0.002：0.421 \ pm0.002 $。这里的$ a $是位于银河飞机上的半大轴，指向我们。 $ b $和$ c $是两个半少量轴，前者躺在银河飞机上，后来垂直于它。 $ b $的值较小，而$ a $与以galacto为中心的距离获得的$ a $ $ r \ ge 2.0 $ 〜kpc表示存在凸起的凸起的结构，其条形角为$ 22^{\ circ} .006 \ pm2^{\ pm2^{\ circ} .078 $。
We present an analysis of high latitude $δ$ Scuti stars ($\left|b\right|> 1^{\circ}$) in the Galactic bulge region ($-8^{\circ}.3< l<9^{\circ}.4$) using a clean sample of the photometric data of $7,440$ stars recently released by the OGLE-IV project. The geometrical parameters of the bulge are determined based on Maximum Likelihood (ML) analysis in five-dimensional parameter space. More refined values of these parameters as well as their uncertainties are obtained from a fully Bayesian Markov Chain Monte Carlo (MCMC) analysis. Approximating the bulge as an ellipsoid, the distribution of the number density of stars as a function of Galacto-centric distance has been modelled using three distribution functions: two Exponential ($\rm E_{1},\rm E_{2}$) types and one Gaussian ($\rm G$) type. Based on the AIC and BIC values, the exponential model $\rm E_{1}$ is chosen as the best statistical model for the parameter values obtained from the MCMC analysis. The MCMC analysis yields the following results: the mean distance to the Galactic center (GC) is found to be $R_{0}=8.034\pm0.012_{\rm stat}\pm0.586_{\rm sys}$ kpc; the bulge $δ$ Scuti distribution has a triaxial shape with normalized ($a\equiv1$) axes ratios ($a:b:c$) as $1.000\pm 0.005:0.348\pm0.002:0.421\pm0.002$. Here $a$ is the semi-major axis lying in the Galactic plane and pointing towards us; $b$ and $c$ are the two semi-minor axes, the former lying in the Galactic plane and the later perpendicular to it. Smaller values of $b$ as compared to $a$ obtained for Galacto-centric distances $R\ge 2.0$~kpc indicate the presence of a bar-like structure of the bulge with a bar angle of $22^{\circ}.006\pm2^{\circ}.078$.
