发表机构
Purple Mountain Observatory, Chinese Academy of Sciences; University of Michigan; Tsinghua University; University of Massachusetts, Amherst（中国科学院紫金山天文台; 密歇根大学; 清华大学; 马萨诸塞大学阿默斯特分校）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
通过联合X射线和SZ观测发现内晕存在隐藏的X射线暗淡但热压显著的CGM成分，其填充因子极小，导致单相分析严重低估重子质量和热能。
AI 中文摘要
大质量星系预期拥有包含其相当一部分重子和反馈能量的热气体延展晕。X射线观测探测这种星系周介质（CGM）中致密、X射线明亮的成分，而热Sunyaev-Zel'dovich（SZ）效应则通过其积分热压对较低密度气体同样敏感。我们利用来自XART-ATOMS（X射线探测吸积储库转移至大质量旋涡星系大气层）计划的深度XMM-Newton对NGC 4594的观测，结合多个独立的基于Planck的SZ重建，首次对一个巨大孤立盘状星系进行了空间分辨的联合X射线与SZ分析。在内晕中测得的SZ信号似乎超过了由X射线推导的气体性质所预测的值，即使考虑了主要的系统不确定性。我们的首选解释是，一个额外的较低密度CGM成分对观测到的软X射线发射贡献甚微，但携带了可观的热压。在近似压力平衡的简单两相模型下，最可能的X射线与SZ比值表明，探测到的X射线发射气体仅占据晕体积的一小部分，在r~50 kpc附近特征填充因子为f_X ~ (4-6)x10^-3。如此小的填充因子意味着单相X射线分析可能将热CGM中的重子质量低估约2.5倍，而CGM的热能含量则被低估约一个数量级。在X射线光谱中未探测到额外成分要求其非常热和/或在空间上延展，因此在软X射线发射中很弱。这些结果支持存在一个“隐藏的”、X射线暗淡的较热晕成分，而包括非热贡献在内的其他解释也不能排除。
英文摘要
Massive galaxies are expected to host extended halos of hot gas that contain a substantial fraction of their baryons and feedback energy. X-ray observations probe the dense, X-ray-bright component of this circumgalactic medium (CGM), while the thermal Sunyaev-Zel'dovich (SZ) effect is also sensitive to lower-density gas through its integrated thermal pressure. We present the first spatially resolved joint X-ray and SZ analysis of a massive isolated disk galaxy, using deep XMM-Newton observations of NGC 4594 from the X-raying the Accretion Reservoir Transferred to the ATmosphere Orbiting a Massive Spiral (XART-ATOMS) program, together with multiple independent Planck-based SZ reconstructions. The measured SZ signal in the inner halo appears to exceed the value predicted from the X-ray-derived gas properties, even after accounting for major systematic uncertainties. Our preferred interpretation is that an additional lower-density CGM component contributes little to the observed soft X-ray emission but carries substantial thermal pressure. Under a simple two-phase model in approximate pressure equilibrium, the most probable X-ray-to-SZ ratio implies that the detected X-ray-emitting gas occupies only a small fraction of the halo volume, with a characteristic filling factor of f_X ~ (4-6)x10^-3 near r~50 kpc. Such a small filling factor implies that single-phase X-ray analyses can underestimate the baryon mass contained in the hot CGM by a factor of ~2.5, while the thermal energy content of the CGM is underestimated by about one order of magnitude. The non-detection of the additional component in the X-ray spectra requires it to be very hot and/or spatially extended, so weak in the soft X-ray emissions. These results favor the presence of a "hidden" X-ray-faint hotter halo component, while alternative interpretations, including a nonthermal contribution, are not excluded.
Comments11 pages, 6 figures, 1 table, published by ApJ on September 18. Related press release: http://english.pmo.cas.cn/research/rp/202609/t20260915_1200453.html
Journal refJ.-T. Li, et al., 2026, ApJ, 1009, 72
