arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1702.02157astro-ph.HE
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使用朱雀搜索A2744周围的PDKEEPAAA

Search for WHIM around A2744 using Suzaku

Shiho Hattori, Naomi Ota, Yu-Ying Zhang, Hiroki Akamatsu, Alexis Finoguenov

摘要:

本文介绍了在$z=0.3$上观测到的一个星系团A2744周围区域的朱雀卫星观测结果。为了寻找温暖炽热的星系际介质(WHIM)的氧发射线,我们分析了来自两个东北区域的X射线光谱,从2.2-3.3和3.3-4.4 Mpc的集群的中心,这提供了第一个测试的WHIM附近的典型吸积激波半径($\sim 2r_{200}$)流体动力学模拟预测。对于2.2-3.3 Mpc区域,当我们在光谱模型中包括OVII和OVIII线时,光谱拟合显著改善(99.2%显著性)。在3.3-4.4 Mpc区域获得了相当的WHIM表面亮度,OVIII线的红移与$z=0.3$在误差范围内一致。目前的结果支持所观察到的软X射线发射起源于WHIM。然而,考虑到统计和系统的不确定性,在东北地区的OVIII检测是边缘的。在2.2-3.3,3.3-4.4 Mpc区域测量了${\rm 10^{-7} photons\,cm^{-2}s^{-1}arcmin^{-2}}$中OVIII线的表面亮度为$2.7\pm 1.0$,$2.1 \pm 1.2$,分别给出了$δ= 319 (<443)$,$283 (<446)$重子过密度的上限。这与以前对星系团外围的观测及其理论预测是相当的。对Athena X-IFU微量热计用于WHIM检测的前景进行了简要讨论。此外,我们还推导了A2744的ICM温度分布,以检测在无线电遗迹的位置明显的不连续性。这表明星系团已经经历了强烈的冲击加热的质量吸积沿暗条。

英文摘要:

We present the results from the Suzaku satellite of the surrounding region of a galaxy cluster, A2744, at $z=0.3$. To search for oxygen emission lines from the warm-hot intergalactic medium (WHIM), we analyzed X-ray spectra from two northeast regions 2.2-3.3 and 3.3-4.4 Mpc from the center of the cluster, which offers the first test on the presence of a WHIM near the typical accretion shock radius ($\sim 2r_{200}$) predicted by hydrodynamical simulations. For the 2.2-3.3 Mpc region, the spectral fit significantly (99.2% significance) improved when we include OVII and OVIII lines in the spectral model. A comparable WHIM surface brightness was obtained in the 3.3-4.4 Mpc region and the redshift of OVIII line is consistent with $z=0.3$ within errors. The present results support that the observed soft X-ray emission originated from the WHIM. However, considering both statistical and systematic uncertainties, OVIII detection in the northeast regions was marginal. The surface brightness of the OVIII line in ${\rm 10^{-7} photons\,cm^{-2}s^{-1}arcmin^{-2}}$ was measured to be $2.7\pm 1.0$, $2.1 \pm 1.2$ for the 2.2-3.3, 3.3-4.4 Mpc regions, giving the upper limit on the baryon overdensity of $δ= 319 (<443)$, $283 (<446)$, respectively. This is comparable with previous observations of cluster outskirts and their theoretical predictions. The future prospect for WHIM detection using the Athena X-IFU micro-calorimeter is briefly discussed here. In addition, we also derived the ICM temperature distribution of A2744 to detect a clear discontinuity at the location of the radio relic. This suggests that the cluster has undergone strong shock heating by mass accretion along the filament.

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