论文标题
MKW4星系组的Suzaku和Chandra联合观察到病毒半径
Joint Suzaku and Chandra observations of the MKW4 galaxy group out to the virial radius
论文作者
论文摘要
我们提出了MKW4的suzaku和Chandra观察结果。 MKW4的全球温度为1.6 KEV，是已在X射线中映射到病毒半径的最小星系组之一。我们测量其气体性质从其中心到北部，东部和东北方向的病毒半径。它的熵配置文件遵循$ \ propto r^{1.1} $在r $ _ {500} $和r $ _ {200} $之间的权力，正如从纯粹的重力结构形成模型所预期的那样。 MKW4郊区的表现良好的熵剖面不利于该系统中离子和电子之间的气体结块或热量非平衡的存在。我们在r $ _ {200} $上的封闭式巴属分数为11％，非常小于宇宙巴属分数15％。我们注意到，对于r $ _ {200} $的封闭式气体分数对于组中的组比文献中现有研究的集群小。银河系组（例如MKW4）的低bary部分表明，它们的较浅的重力势可能使它们更容易因AGN反馈或银河风而造成重子损失。我们发现，MKW4郊区各种气体特性的方位角散射明显低于其他系统，这表明MKW4是球形对称和高度放松的系统。
We present joint Suzaku and Chandra observations of MKW4. With a global temperature of 1.6 keV, MKW4 is one of the smallest galaxy groups that have been mapped in X-rays out to the virial radius. We measure its gas properties from its center to the virial radius in the north, east, and northeast directions. Its entropy profile follows a power-law of $\propto r^{1.1}$ between R$_{500}$ and R$_{200}$ in all directions, as expected from the purely gravitational structure formation model. The well-behaved entropy profiles at the outskirts of MKW4 disfavor the presence of gas clumping or thermal non-equilibrium between ions and electrons in this system. We measure an enclosed baryon fraction of 11% at R$_{200}$, remarkably smaller than the cosmic baryon fraction of 15%. We note that the enclosed gas fractions at R$_{200}$ are systematically smaller for groups than for clusters from existing studies in the literature. The low baryon fraction of galaxy groups, such as MKW4, suggests that their shallower gravitational potential well may make them more vulnerable to baryon losses due to AGN feedback or galactic winds. We find that the azimuthal scatter of various gas properties at the outskirts of MKW4 is significantly lower than in other systems, suggesting that MKW4 is a spherically symmetric and highly relaxed system.
