AI 中文总结
本研究利用改进的ASKAP和MWA射电图像，通过模型拟合揭示NGC 253中心为平流主导、外围为扩散主导的CRE传输模式，证实低频射电观测可用于探测CRE传输与星系外流。
AI 中文摘要
近侧视星暴星系NGC 253呈现出延展的多波段晕发射，使其成为研究盘-晕传输的理想实验室。我们提供了改进后的ASKAP 943 MHz和MWA 216 MHz总强度图像，分辨率分别为13角秒和45角秒，均方根噪声水平分别为16 μJy/束和1 mJy/束。扣除热发射后，我们用一维平流和扩散模型拟合了垂直同步加速辐射强度和谱指数轮廓。ASKAP图像揭示了西北射电 spur 中一个环状结构，延伸至盘上方约9千秒差距处，而东南 spur 达到约8千秒差距。垂直轮廓在中心区域用指数分量拟合最佳，在外围区域用高斯分量拟合最佳，表明中心区域为平流主导的宇宙射线（CRE）传输，外围区域为扩散主导。在中心区域，平流速度随高度呈指数增长，在约5.5千秒差距处达到估计的逃逸速度。其与恒星形成区和X射线发射区的空间对应关系表明，CRE平流追踪磁化外流的整体运动。在约5.5千秒差距以下，热、磁、宇宙射线和动压的组合超过估计的引力压，与星系风的加速一致。这些结果证明了灵敏的低频射电观测在探测CRE传输和星系外流方面的能力。
英文摘要
The nearly edge-on starburst galaxy NGC 253 exhibits extended multiwavelength halo emission, making it an ideal laboratory for studying disk-halo transport. We present improved ASKAP 943 MHz and MWA 216 MHz total-intensity images with resolutions of 13 and 45 arcsec and rms noise levels of 16 $μ$Jy beam$^{-1}$ and 1 mJy beam$^{-1}$, respectively. After subtracting the thermal emission, we fitted the vertical synchrotron emission intensity and spectral-index profiles with one-dimensional advection and diffusion models. The ASKAP image reveals a loop-like structure in the northwestern radio spur extending to $\sim9$ kpc above the disk, while the southeastern spur reaches $\sim8$ kpc. The vertical profiles are best fitted by exponential components in the central region and Gaussian components in the outer regions, indicating advection-dominated CRE transport in the center and diffusion elsewhere. In the central region, the advection speed increases exponentially with height and reaches the estimated escape speed at about 5.5 kpc. The spatial correspondence with star-forming and X-ray-emitting regions indicates that CRE advection traces the bulk motion of the magnetized outflow. Below $\sim5.5$ kpc, the combined thermal, magnetic, cosmic-ray, and ram pressures exceed the estimated gravitational pressure, consistent with acceleration of the galactic wind. These results demonstrate the power of sensitive low-frequency radio observations for probing CRE transport and galactic outflows.
Comments20 pages, 20 figures and 3 tables. Accepted for publication in A&A
