AI 中文总结
针对积分场吸收线层析成像中空间像素中心无法代表吸收流量起源的问题，提出流量加权坐标与撞击参数的流量贡献形式主义，可更准确恢复周介质径向柱密度轮廓，结果鲁棒性优于传统空间像素中心法。
AI 中文摘要
引力弧等延展背景源的积分场单元（IFU）光谱学，提供了穿过前景星系周介质（CGM）的众多间距紧密的吸收视线。然而，源的延展范围和点扩散函数（PSF）导致的模糊，使得每个空间像素（spaxel）积分的光来自比其自身更大的区域，因此通常采用的空间像素中心并不能代表吸收流量的起源位置。基于高分辨率成像的信息，我们引入了流量贡献形式主义，通过定义流量加权坐标和撞击参数来重建每个空间像素中流量的空间起源。使用基于真实引力弧构型构建的数据驱动模拟，我们表明，空间像素中心与流量加权位置的位移满足$|\Delta\mathbf{x}| \propto \theta_{\rm PSF}(1-f)$，其中$f$为空间像素-源重叠比例，且由此产生的撞击参数偏差随透镜放大率按$\text{mu}^{-1/2}$缩放。这些位移对于弧外空间像素最大，并会使径向柱密度轮廓变平，还会引入一种由几何驱动的相干散射，这种散射模拟了CGM的固有结构，且无法通过更严格的空间像素选择或更精细的空间分箱消除。在相同不确定度下，空间像素中心坐标的残差约为噪声水平的两倍（$\text{chi}^2_\nu \sim 4$），而流量加权坐标则能在不确定度范围内恢复输入轮廓（$\text{chi}^2_\nu \sim 1$），且对$\text{pm}10\\%$的PSF误标定仍具有鲁棒性。我们提出的方法为层析成像研究提供了更具依据且易于采用的框架，既可作为主要分析手段，也可作为对空间像素中心结果的鲁棒性检验。
英文摘要
Integral-field-unit (IFU) spectroscopy of extended background sources, such as gravitational arcs, delivers many closely spaced absorption sightlines through the circumgalactic medium (CGM) of foreground galaxies. However, the source extent and smearing through the point spread function (PSF) cause each spaxel to integrate light from a region larger than itself. The usually adopted geometric spaxel centre is therefore not representative of where the absorbed flux originates. Informed by high-resolution imaging, we introduce a flux-contribution formalism that reconstructs the spatial origin of the flux in each spaxel by defining flux-weighted coordinates and impact parameters. Using a data-driven simulation built on a real gravitational-arc configuration, we show that spaxel centres are displaced from the flux-weighted positions by $|Δ\mathbf{x}| \propto θ_{\rm PSF}(1-f)$, with $f$ the spaxel-source overlap fraction, and that the resulting impact-parameter bias scales with the lensing magnification as $μ^{-1/2}$. These offsets are largest for off-arc spaxels and flatten the radial column-density profiles. They also inject a coherent geometry-driven scatter that mimics intrinsic CGM structure and that is removed neither by a tighter spaxel selection nor by a finer spatial binning. For identical uncertainties, the spaxel-centre coordinates leave residuals of about twice the noise level ($χ^2_ν\sim 4$), whereas the flux-weighted coordinates recover the input profile to within the uncertainties ($χ^2_ν\sim 1$) and remain robust to a PSF misspecification of $\pm 10\%$. The method we propose provides a better-motivated and readily adoptable framework for tomographic studies, whether as the primary analysis or as a robustness check on spaxel-centre results.
CommentsAccepted for publication in A&A
