发表机构
Korea Astronomy and Space Science Institute; Department of Astronomy and Space Science, University of Science and Technology; Max-Planck-Institut für Astrophysik; Astronomisches Rechen-Institut, Zentrum für Astronomie, Universität Heidelberg（韩国天文与空间科学研究所; 科学技术大学天文与空间科学系; 马克斯·普朗克天体物理学研究所; 海德堡大学天文学计算研究所天文学中心）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过3D蒙特卡洛模拟揭示星系周介质旋转对Lyα谱线峰间距和空间分辨特征的影响，指出旋转与柱密度存在简并，强调空间分辨观测对区分旋转与辐射转移效应的必要性。
AI 中文摘要
氢莱曼阿尔法（Ly$\alpha$）是星系周介质（CGM）中一条显著的发射线。由于其共振性质，Ly$\alpha$携带着冷CGM的物理性质和运动学信息。特别是，CGM旋转可以改变Ly$\alpha$峰间距，而峰间距常被解释为中性氢柱密度的示踪。我们展示了在类似CGM的旋转介质中进行的3D蒙特卡洛Ly$\alpha$辐射转移模拟，并考察了发射谱如何依赖于旋转速度（$V_{\rm rot}$）、中性氢柱密度（$N_{\rm HI}$）、观测角度、团块性和内禀源宽度。我们发现旋转使积分谱展宽并增大峰间距，当旋转多普勒位移主导频率扩散时，观测角度依赖性最强。在高$N_{\rm HI}$下，大量散射降低了积分谱对旋转的敏感性，导致$V_{\rm rot}$与$N_{\rm HI}$之间产生简并。因此，仅凭Ly$\alpha$峰间距在旋转介质中会高估$N_{\rm HI}$。空间分辨的晕光谱提供了更清晰的诊断：旋转介质的两侧显示出与最后一次散射气体的视线速度相关的系统性红移和蓝移不对称性。这种由旋转驱动的特征也可能贡献于通常被解释为内流或外流的速度图模式，强调在空间分辨Ly$\alpha$观测中需要考虑旋转。我们进一步表明，主要特征在简单的团块介质中仍然存在，而晕特征对内禀源宽度基本不敏感。我们的结果表明，空间分辨Ly$\alpha$观测对于区分CGM旋转与辐射转移效应至关重要。
英文摘要
Hydrogen Lyman-alpha (Ly$α$) is a prominent emission line from the circumgalactic medium (CGM). Due to its resonant nature, Ly$α$ carries imprints of the physical properties and kinematics of the cold CGM. In particular, CGM rotation can modify the Ly$α$ peak separation, which is often interpreted as a tracer of H I column density. We present 3D Monte Carlo Ly$α$ radiative-transfer simulations in a CGM-like rotating medium and examine how the emergent spectra depend on rotational velocity ($V_{\rm rot}$), H I column density ($N_{\rm HI}$), viewing angle, clumpiness, and intrinsic source width. We find that rotation broadens the integrated spectra and increases the peak separation, with the strongest viewing-angle dependence when rotational Doppler shifts dominate over frequency diffusion. At high $N_{\rm HI}$, numerous scatterings reduce the sensitivity of integrated spectra to rotation, producing a degeneracy between $V_{\rm rot}$ and $N_{\rm HI}$. Consequently, Ly$α$ peak separation alone can overestimate $N_{\rm HI}$ in a rotating medium. Spatially resolved halo spectra provide a clearer diagnostic: opposite sides of the rotating medium show systematic redshifted and blueshifted asymmetries associated with the line-of-sight velocity of the last-scattering gas. Such rotation-driven signatures can also contribute to velocity-map patterns often interpreted in terms of inflow or outflow, highlighting the need to consider rotation in spatially resolved Ly$α$ observations. We further show that the main signatures persist in simple clumpy media, while the halo signatures are largely insensitive to the intrinsic source width. Our results demonstrate that spatially resolved Ly$α$ observation is essential for disentangling CGM rotation from radiative-transfer effects.
Comments14 pages, 15 figures. Submitted to MNRAS
