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arXiv 2606.08097astro-ph.COastro-ph.HE
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XRISM对Abell 1795的观测:低湍流和共振散射的证据

XRISM Observations of Abell 1795: Evidence for Low Turbulence and Resonant Scattering

University of Arkansas(阿肯色大学);Massachusetts Institute of Technology(麻省理工学院);University of Waterloo(滑铁卢大学);University of Nottingham(诺丁汉大学);Japan Aerospace Exploration Agency (JAXA)(日本宇宙航空研究开发机构);Tokyo Metropolitan University(东京都立大学);University of Maryland, College Park(马里兰大学帕克分校);NASA / Goddard Space Flight Center(美国国家航空航天局戈达德太空飞行中心)
Arnab Sarkar, Eric D. Miller, Brian McNamara, Helen Russell, Kotaro Fukushima, Mark Bautz, Yutaka Fujita, Catherine E. Grant, François Mernier, Michael A. McDon… 展开作者

Arnab Sarkar, Eric D. Miller, Brian McNamara, Helen Russell, Kotaro Fukushima, Mark Bautz, Yutaka Fujita, Catherine E. Grant, François Mernier, Michael A. McDonald, Naomi Ota, Ayşegül Tümer, Daniel Wik

AI总结:

利用XRISM/Resolve对冷核星系团Abell 1795进行高分辨率X射线光谱观测,发现视线速度弥散度从核心到320 kpc递减,中心区域体速度极低,不支持冷却尾流模型而支持AGN抬升起源,并检测到Fe XXV w线的共振抑制。

摘要:

我们展示了利用XRISM/Resolve对冷核星系团Abell 1795进行的高分辨率X射线光谱观测。该星系团通过两次深度指向观测:一次225 ks的中心曝光和一次113 ks的北部曝光,延伸至距星系团中心320 kpc的投影半径。单温度拟合揭示了视线速度弥散度的清晰径向梯度,从核心的114 ± 11 km/s下降到320 kpc处的68 ± 39 km/s。中心区域的体速度非常低(22 ± 12和7 ± 21 km/s),表明最亮星系团星系(BCG)与星系团内介质(ICM)之间没有显著的相对运动。鉴于中心区域包括向南延伸的冷气体尾,这一结果不利于“冷却尾流”模型,而支持AGN抬升起源。我们发现非热压比随半径减小,从核心的$P_{\rm NT}/P_{\rm T}\approx2\\%$下降到330 kpc处的约0.6%,表明A1795北部的ICM基本处于静止状态。双温度和分裂能段(2-4 keV和6-7 keV)拟合在中心$<1.5'$区域内识别出两个气体相,为星系团核心的多相气体提供了有力证据。我们检测到中心光学厚的Fe XXV $w$线约14%的共振抑制。此外,我们观察到Fe XXV $y$线通量相对于模型存在显著过剩。考虑原子数据的不确定性后,这一差异减小,表明原子数据不确定性可能对观测到的剩余通量有贡献。

英文摘要:

We present high-resolution X-ray spectroscopic observations of the cool-core galaxy cluster Abell~1795 obtained with XRISM/Resolve. The cluster was observed with two deep pointings: a 225 ks central exposure and a 113 ks northern exposure, extending to a projected radius of 320 kpc from the cluster center. Single-temperature fits reveal a clear radial gradient in the line-of-sight velocity dispersion, decreasing from 114 $\pm$ 11 km/s in the core to 68 $\pm$ 39 km/s at 320 kpc. The bulk velocities in the central regions are very low (22 $\pm$ 12 and 7 $\pm$ 21 km/s), indicating no significant relative motion between the brightest cluster galaxy (BCG) and the intracluster medium (ICM). Given that the central region includes the southward extending cool gas tail, this result disfavors the ``cooling-wake'' scenario and instead supports an AGN-uplift origin. We find that the nonthermal pressure fraction decreases with radius, from $P_{\rm NT}/P_{\rm T}\approx2\%$ in the core to $\sim0.6\%$ at 330 kpc, suggesting that the northern ICM of A1795 is largely quiescent. Two-temperature and split energy-band (2--4 keV and 6--7 keV) fits identify two gas phases within the central $<1.5'$ region, providing strong evidence for multiphase gas in the cluster core. We detect a $\sim14\%$ resonant suppression of the optically thick Fe XXV $w$ line in the center. Additionally, we observe a significant excess in the Fe XXV $y$ line-flux relative to models. Accounting for uncertainties in the atomic data reduces this discrepancy, suggesting that atomic data uncertainties may contribute to the observed residual flux.

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