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首页> 外文期刊>PASJ: Publications of the Astronomical Society of Japan >X-ray study of the outer region of Abell 2142 with Suzaku
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X-ray study of the outer region of Abell 2142 with Suzaku

机译：朱雀将对Abell 2142外部区域进行X射线研究

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摘要

We observed outer regions of a bright cluster of galaxies, A2142, with Suzaku. Temperature and brightness structures were measured out to the virial radius (r _(200)) with good sensitivity. We confirmed a temperature drop from 9 keV around the cluster center to about 3.5 keV at r _(200), with the density profile well approximated by the β-model with β = 0.85. Within 0.4 r _(200), the entropy profile agrees with r ~(1.1), as predicted by the accretion shock model. The entropy slope becomes flatter in the outer region and negative around r _(200). These features suggest that the intracluster medium in the outer region is out of thermal equilibrium. Since the relaxation timescale of electron-ion Coulomb collisions is expected to be longer than the elapsed time after shock heating at r _(200), one plausible reason for the low entropy is a low electron temperature compared to that of ions. Other possible explanationswould be gas clumpiness, turbulence and bulk motions of the ICM. We also searched for a warm-hot intergalactic medium around r _(200), and set an upper limit on the oxygen line intensity. Assuming a line-of-sight depth of 2 Mpc and oxygen abundance of 0.1 solar, the upper limit of an overdensity is calculated to be 280 or 380, depending on the foreground assumption.
机译：我们观察到了朱雀与一个明亮的星系团A2142的外部区域。温度和亮度结构以良好的灵敏度测量到病毒半径（r _（200））。我们确认了温度从团簇中心附近的9 keV下降到r _（200）处的约3.5 keV，密度分布通过β模型很好地近似为β= 0.85。在0.4 r _（200）内，熵曲线与r〜（1.1）一致，如增生冲击模型所预测的那样。熵斜率在外部区域变得更平坦，在r _（200）附近为负。这些特征表明，外部区域的集群内介质没有达到热平衡。由于预计电子离子库仑碰撞的弛豫时间尺度将比在r _（200）处进行冲击加热后经过的时间更长，因此，低熵的一个可能原因是与离子相比电子温度低。其他可能的解释可能是ICM的气体团块，湍流和整体运动。我们还搜索了r _（200）附近的热星际介质，并为氧气线强度设置了上限。假设视线深度为2 Mpc，氧气丰度为0.1太阳，则根据前景假设，计算出的密度上限为280或380。

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