发表机构
Xiangtan University; Institute of High Energy Physics, Chinese Academy of Sciences; Beijing Normal University（湘潭大学; 中国科学院高能物理研究所; 北京师范大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
利用EP-FXT深度观测，研究冷核星系团A478至R200的热力学性质与方位不对称性，发现其全球准静态但局部受气体晃动扰动，影响质量估计。
AI 中文摘要
我们利用爱因斯坦探针后续X射线望远镜（EP-FXT）的深度观测，研究了冷核星系团Abell 478（A478）从中心到R200的气体分布和热力学性质，并考察了其方位不对称性以及局部动力学扰动对流体静力学质量估计的影响。我们推导了表面亮度、温度、电子密度、压力、熵和总质量分布。表面亮度分布由双β模型很好地描述，而温度分布显示出典型的冷核行为，中心温度较低，向中等半径处上升，并在外围逐渐下降。流体静力学质量分布由Navarro-Frenk-White模型很好地拟合，得到R200=2082±95 kpc和M200=(1.12±0.15)×10^15 M_sun，表明该星系团在全球尺度上接近准静态平衡。尽管整体结构规则，但存在明显的方位不对称性。西南扇区在中等和大半径处表现出较低的温度、较高的密度和较低的熵，并伴有与冷锋候选体一致的迹象。结合二维温度分布，这些特征表明存在局部动力学扰动，可能与气体晃动有关。因此，A478在全球范围内是弛豫的，但在局部受到扰动，表明即使在看似规则的冷核星系团中，非平衡结构仍可能影响热力学测量和流体静力学质量估计。
英文摘要
We use deep observations from the Einstein Probe Follow-up X-ray Telescope (EP-FXT) to investigate the gas distribution and thermodynamic properties of the cool-core galaxy cluster Abell 478 (A478) from the center out to $R_{200}$, and to examine its azimuthal asymmetry and the influence of local dynamical disturbances on hydrostatic mass estimates. We derive the surface-brightness, temperature, electron-density, pressure, entropy, and total mass profiles. The surface-brightness distribution is well described by a double-$β$ model, while the temperature profile shows the characteristic cool-core behavior, with a cool center, a rise toward intermediate radii, and a gradual decline in the outskirts. The hydrostatic mass profile is well fitted by a Navarro-Frenk-White model, yielding $R_{200}=2082\pm95$ kpc and $M_{200}=(1.12\pm0.15)\times10^{15}\,M_\odot$, indicating that the cluster is close to quasi-static equilibrium on global scales. Despite the globally regular structure, clear azimuthal asymmetry is present. The SW sector shows lower temperatures, higher densities, and lower entropies at intermediate and large radii, together with signatures consistent with a cold-front candidate. Combined with the two-dimensional temperature distribution, these features suggest local dynamical disturbance, likely associated with gas sloshing. A478 is therefore globally relaxed but locally disturbed, demonstrating that nonequilibrium structures can still affect thermodynamic measurements and hydrostatic mass estimates even in an apparently regular cool-core cluster.
CommentsAccepted for publication in Astronomy & Astrophysics. 17 pages, 11 figures
