发表机构
California Institute of Technology; The Observatories of the Carnegie Institution for Science; Tsinghua University; The University of Chicago; Princeton University; University of Toronto（加州理工学院; 卡内基科学研究所天文台; 清华大学; 芝加哥大学; 普林斯顿大学; 多伦多大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文利用IFS发射线图谱的投影效应，通过速度色散比约束冷CGM的视线深度，发现其与投影延展相当，为三维CGM结构提供新探针。
AI 中文摘要
冷（T~$10^4$ K）星系周介质（CGM）的三维几何结构——视线方向深度和离散团块数量——目前约束很差。现有的推断主要来自类星体吸收线统计，但这些笔形束探针提供的空间和运动学信息有限。在此，我们表明当考虑投影效应时，来自积分场光谱仪（IFS）观测的空间分辨发射线图谱为冷CGM几何提供了补充性的新约束。对CGM星云样本的观测得到了视线方向和天平面方向速度色散的测量值，其比值$\sigma_{\rm los}/\sigma_{\rm pos}$范围约为1到2.5。通过使用各向同性湍流的直接数值模拟，并将其投影到不同深度$L_{\rm los}$的发射薄板中，我们表明比值$\sigma_{\rm los}/\sigma_{\rm pos}$使我们能够探测$L_{\rm los}/L_{\rm neb}$，其中$L_{\rm neb}$是星云在天平面上的延展范围。我们发现推断的视线方向深度通常约为0.1-$5\\,L_{\rm neb}$，表明这些星云在深度和投影延展上大致相当。尽管冷CGM本质上是团块状的，但在当前IFS数据分辨率下，每个波束聚合了足够多的团块，使得投影色散比接近其体积填充值。因此，发射运动学除了与吸收线巡天推断的团块发生率一致外，对详细的团块构型提供的信息很少。这些发现为姊妹论文（论文II）中发展的湍流诊断提供了理论框架。这些论文共同展示了IFS发射线运动学如何为三维CGM提供定量探针，与吸收线和新兴的FRB方法互补。
英文摘要
The three-dimensional geometric structure of the cool (T~$10^4$ K) circumgalactic medium (CGM) -- the line-of-sight depth and the number of discrete clumps -- is poorly constrained. Existing inferences come predominantly from quasar absorption-line statistics, but these pencil-beam probes provide limited spatial and kinematic information. Here we show that spatially resolved emission-line maps from integral field spectrograph (IFS) observations provide complementary, novel constraints on cool CGM geometry when projection effects are accounted for. Observations of a sample of CGM nebulae yield measurements of the line-of-sight and the plane-of-sky velocity dispersions, with ratios $σ_{\rm los}/σ_{\rm pos}$ ranging from ~1 to ~2.5. Using direct numerical simulations of isotropic turbulence projected through emitting slabs of varying depth $L_{\rm los}$, we show that the ratio $σ_{\rm los}/σ_{\rm pos}$ allows us to probe $L_{\rm los}/L_{\rm neb}$, where $L_{\rm neb}$ is the nebular extent on the plane of the sky. We find that the inferred line-of-sight depth is typically ~0.1-$5\,L_{\rm neb}$, indicating that these nebulae are broadly comparable in depth and projected extent. Although the cool CGM is intrinsically clumpy, at the current IFS data resolution, each beam aggregates enough clumps that the projected dispersion ratio approaches its volume-filling value. Consequently, the emission kinematics provide little additional information on the detailed clump configuration beyond consistency with the clump incidence rates inferred from absorption-line surveys. These findings serve as a theoretical framework for the turbulence diagnostics developed in the companion paper (Paper II). Together, these papers demonstrate how IFS emission-line kinematics can provide a quantitative probe of the 3D CGM, complementary to absorption-line and emerging FRB approaches.
Comments20 pages, 5 figures, submitted to AAS Journals
