标题： 星系团中 ICM 密度分布三维重建的球面对称偏差 显示英文标题

标题： Spherical bias on the 3D reconstruction of the ICM density profile in galaxy clusters

摘要： X射线观测通常用于推导星系团的热动力学性质（如密度和温度）的径向分布。然而，观测只能提供球面投影上的量，因此需要假设星系团内介质（ICM）的三维分布。 通常假设球形几何结构。 本文的目标是确定由于这一近似方法在重建星系团样本的ICM密度径向分布以及密度分布的固有散度时产生的偏差，当未屏蔽星系团子结构时。 我们使用了来自“三百项目”的98个模拟星系团，这些星系团已知其三维ICM分布。对于每个星系团，我们沿40条不同的视线投影模拟了40次不同的观测。我们从每次观测中提取了ICM密度剖面，并假设ICM呈球形分布。然后我们考虑了每个视线方向上样本的平均密度剖面，并将其与模拟提供的三维密度剖面进行比较。通过观察值与输入值的比值来得出密度剖面的球形偏差。我们也通过相同的程序研究了密度剖面分布的固有散度偏差。我们发现密度剖面的偏差，$b_n$，在$R\lesssim R_{500}$的情况下小于$10\%$，而在更大的半径下增加到$\sim 50\%$。固有散度剖面的偏差，$b_s$，在$R\approx R_{500}$处达到$\approx 100\%$。 被分析量上的偏差强烈依赖于天体的形态：对于不存在大规模次结构的星系团，$b_n$和$b_s$减小为原来的二分之一，相反，对于存在大规模次结构的系统，$b_n$和$b_s$显著增加。 显示英文摘要

摘要： X-ray observations of galaxy clusters are routinely used to derive radial distributions of ICM thermdynamical properties such as density and temperature. However, observations allow us to access quantities projected on the celestial sphere only, so that an assumption on the 3D distribution of the ICM is necessary. Usually, spherical geometry is assumed. The aim of this paper is to determine the bias due to this approximation on the reconstruction of ICM density radial profile of a clusters sample and on the intrinsic scatter of the density profiles distribution, when clusters substructures are not masked. We used 98 simulated clusters for which we know the 3D ICM distribution drawn from The Three Hundred project. For each cluster we simulated 40 different observations by projecting the cluster along 40 different lines of sight. We extracted the ICM density profile from each observation assuming the ICM to be spherical distributed. For each line of sight we then considered the mean density profile over the sample and compared it with the 3D density profile given by the simulations. The spherical bias on the density profile is derived by considering the ratio between the observed and the input quantities. We also study the bias on the intrinsic scatter of the density profile distribution performing the same procedure. We find a bias on the density profile, $b_n$, smaller than $10\%$ for $R\lesssim R_{500}$ while it increases up to $\sim 50\%$ for larger radii. The bias on the intrinsic scatter profile, $b_s$, reaches a value of $\approx 100\%$ for $R\approx R_{500}$. The bias on both the analysed quantities strongly depends on the morphology of the objects: for clusters that do not show large scale substructures, both $b_n$ and $b_s$ are reduced by a factor 2, conversely for systems that do show large scale substructures both $b_n$ and $b_s$ increase significantly. [abridged]