大质量松弛星系团的平坦密度剖面
The flat density profiles of massive, and relaxed galaxy clusters
摘要：
本文利用Del Popolo（2009）提出的SIM方法，研究了Newman等人（2012 a，b）观测到的7个大质量弛豫星系团MS 2137，A963，A383，A611，A2537，A2667，A2390的总密度和DM密度分布，以及不同数量之间的相关性。与Newman等人（2012 a，b）相似，在半径范围为0.003 - 0.03 $r_{200}$的总密度分布具有与无耗散模拟一致的平均总密度分布。所有聚类的DM曲线的斜率均小于-1。斜率$α$在A2390的情况下具有最大值（包括误差）$α=-0.88$，并且在A2537的情况下具有最小值$α=-0.14$。在半径$< 5-10$ kpc处，重子分量占主导地位，而外部分布则以暗物质为主。我们发现斜率$α$、有效半径、$R_e$和BCG质量之间存在反相关性，核心半径$r_{core}$和$R_e$之间存在相关性。此外，100 kpc（主要是暗物质）的质量与5 kpc（主要是重子）的质量相关。总质量密度分布、DM密度分布和引用的相关性的行为可以在双相情景中理解。在第一个耗散阶段，原BCG的形式，并在第二个无耗散阶段，重子块（坍缩到中心）和DM晕之间的动力学摩擦的密度轮廓的内斜率。简而言之，在簇与簇之间的内部斜率中的大的分散以及斜率、$α$和$R_e$之间的反相关性是由于以下事实：为了具有NFW样的总质量密度分布，在其中心具有更大质量的BCG的簇必须在其中心包含更少的DM。因此，内轮廓具有更平坦的斜率。
英文摘要：
In the present paper, we studied by means of the SIM introduced in Del Popolo (2009), the total and DM density profiles, and the correlations among different quantities, observed by Newman et al. (2012a,b), in seven massive and relaxed clusters, namely MS2137, A963, A383, A611, A2537, A2667, A2390. Similarly to Newman et al. (2012a,b), the total density profile, in the radius range 0.003 - 0.03$r_{200}$, has a mean total density profile in agreement with dissipationless simulations. The slope of the DM profiles of all clusters is flatter than -1. The slope, $α$, has a maximum value (including errors) of $α=-0.88$ in the case of A2390, and minimum value $α=-0.14$ for A2537. The baryonic component dominates the mass distribution at radii $< 5-10$ kpc, while the outer distribution is dark matter dominated. We found an anti-correlation among the slope $α$, the effective radius, $R_e$, and the BCG mass, and a correlation among the core radius $r_{core}$, and $R_e$. Moreover, the mass in 100 kpc (mainly dark matter) is correlated with the mass inside 5 kpc (mainly baryons). The behavior of the total mass density profile, the DM density profile, and the quoted correlations can be understood in a double phase scenario. In the first dissipative phase the proto-BCG forms, and in the second dissipationless phase, dynamical friction between baryonic clumps (collapsing to the center) and the DM halo flattens the inner slope of the density profile. In simple terms, the large scatter in the inner slope from cluster to cluster, and the anti-correlation among the slope, $α$ and $R_e$ is due to the fact that in order to have a total mass density profile which is NFW-like, clusters having more massive BCGs at their centers must contain less DM in their center. Consequently the inner profile has a flatter slope.
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