发表机构
University of Science and Technology of China; Hamburger Sternwarte, Universität Hamburg; Purple Mountain Observatory, Chinese Academy of Sciences; Max-Planck-Institut für Radioastronomie; Qinghai University; Xiangtan University; University of Manitoba（中国科学技术大学; 汉堡天文台，汉堡大学; 中国科学院紫金山天文台; 马克斯·普朗克射电天文研究所; 青海大学; 湘潭大学; 曼尼托巴大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
通过19个侧向星系的多频射电观测，发现非热谱指数随恒星形成率面密度平坦化，斜率受局部动力学环境调制，并量化了宇宙射线电子输运对射电-恒星形成率校准频率依赖性的影响。
AI 中文摘要
射电连续谱辐射示踪了星系中的恒星形成，但宇宙射线电子（CRE）在盘与晕之间的传播使这一联系复杂化。我们呈现了对19个近邻侧向星系的宽波段、空间分辨分析，结合了144 MHz的LOFAR观测、CHANG-ES在1.575、3.0和6.0 GHz的VLA成像，以及混合Hα+22 μm恒星形成率（SFR）图。所有图像均卷积至共同的2.1 kpc分辨率，用于对非热谱指数α_nth和SFR面密度Σ_SFR进行逐像素分析。全部19个星系均表现出统计显著的非热谱平坦化趋势，随Σ_SFR增加，样本中位斜率为0.19_{-0.03}^{+0.09}，该斜率追踪了恒星形成盘中CRE注入与晕中冷却之间的对比。该斜率的星系间离散性与整体星系性质无关，反而似乎受局部动力学环境调制，其中最大的α_nth-Σ_SFR斜率出现在受潮汐扰动的系统中。分辨的射电-SFR斜率从144 MHz的0.57陡增至6 GHz的0.95，在高频接近线性。这一趋势与能量依赖的CRE冷却和输运一致，偏离线性在低频最为显著，此时侧向视线混合了盘面和晕的CRE种群。这些结果对热污染、波束涂抹和谱弯曲具有稳健性。综合起来，我们的分析确立了α_nth作为侧向星系中投影盘-晕CRE输运的观测探针，并量化了这种输运如何重塑分辨射电-SFR校准的频率依赖性。
英文摘要
Radio continuum emission traces star formation in galaxies, but cosmic-ray electron (CRE) propagation between the disk and halo complicates this connection. We present a wide-band, spatially resolved analysis of 19 nearby edge-on galaxies, combining LOFAR observations at 144 MHz with CHANG-ES VLA imaging at 1.575, 3.0, and 6.0 GHz, and hybrid H$α$+22 $μ$m star formation rate (SFR) maps. All maps are convolved to a common 2.1 kpc resolution for pixel-by-pixel analysis of the nonthermal spectral index $α_{\mathrm{nth}}$ and the SFR surface density $Σ_{\mathrm{SFR}}$. All 19 galaxies exhibit statistically significant nonthermal spectral flattening with increasing $Σ_{\mathrm{SFR}}$, with a sample median slope of $0.19_{-0.03}^{+0.09}$ that traces the contrast between CRE injection in the star-forming disk and cooling in the halo. The galaxy-to-galaxy scatter in this slope shows no dependence on global galaxy properties and instead appears to be modulated by the local dynamical environment, with the largest $α_{\mathrm{nth}}$-$Σ_{\mathrm{SFR}}$ slopes appearing in tidally perturbed systems. The resolved radio-SFR slope steepens from 0.57 at 144 MHz to 0.95 at 6 GHz, approaching linearity at high frequencies. This trend is consistent with energy-dependent CRE cooling and transport, with the deviation from linearity most pronounced at low frequencies, where the edge-on line of sight blends midplane and halo CRE populations. These results are robust against thermal contamination, beam smearing, and spectral curvature. Together, our analysis establishes $α_{\mathrm{nth}}$ as an observational probe of projected disk-to-halo CRE transport in edge-on galaxies and quantifies how this transport reshapes the frequency dependence of resolved radio-SFR calibrations.
Comments18 pages, 5 figures (main paper); 11 pages, 19 figures (appendix). Accepted for publication in The Astrophysical Journal
