利用ALMA CMZ探索巡天（ACES）的H40α复合线与连续谱辐射研究中心分子区（CMZ）HII区的电子温度与发射量测
Electron temperature and emission measure of HII regions in the central molecular zone (CMZ) from H40 αrecombination line and continuum emissions by ALMA CMZ Exploration Survey - ACES -
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中文总结 AI 辅助
本研究利用ALMA CMZ探索巡天（ACES）的H40复合线与连续谱数据，应用TeEM方法绘制CMZ的HII区电子温度与发射量测分布，测得CMZ平均电子温度并揭示其空间差异。
中文摘要 AI 辅助
中心分子区（CMZ）的恒星形成活动直接表现为射电连续谱自由-自由辐射（轫致辐射）以及新形成大质量恒星周围HII区的射电复合线辐射。我们通过分析ACES（ALMA CMZ探索巡天）的H40（99.02 GHz）复合线与99.6 GHz连续谱辐射数据（合成束宽分别为2''.45（在8.2 kpc距离处对应0.097 pc）和2''.14），推导CMZ上HII区的整体分布及其基本性质：电子温度（$\te$）与发射量测（EM），进而得到电子密度的二维分布。我们应用“TeEM”方法（$\te$-EM绘图），该方法从输入的连续谱与积分线强度的二维图中生成$\te$与EM图。分析覆盖整个ACES天区，范围为$l\backsim-0^\text{\textdegree}.6$至$+0^\text{\textdegree}.8$，$b\backsim-0^\text{\textdegree}.2$至$+0^\text{\textdegree}.1$，该分析区域是完整的，包含此前已知的HII区，如Sgr B2、Sgr B1、Sickle、Pistol、热丝状体（Bridges）、Sgr A HII区、Minispiral及其他众多已知HII区；因复合线图的信噪比不足，Sgr C未被纳入分析。CMZ的平均电子温度确定为$\te_\text{CMZ}=5872\backsim78$（标准误SE）$\backsim3682$（像素间标准差SD）K（SE为均值的标准误，SD为像素间标准差）。部分HII区，如Sgr B2 Main与Minispiral，表现出较大的离散度及每parsec数千K的内部$\te$梯度。EM分布更为多样，在CMZ内及单个HII区内，其变化幅度达数个数量级，从$\backsim10^5$到$\backsim3\times10^8$ \text{emunit}。
英文摘要
Star formation activity in the Central Molecular Zone (CMZ) directly manifests itself as radio continuum free-free emission (Bremsstrahlung) and radio recombination line emission from HII regions surrounding newly formed massive stars. We derive the overall distribution of the HII regions and their fundamental properties: electron temperature ($\Te$) and emission measure ($EM$), and hence electron density in the form of two dimensional distribution maps over the CMZ by analyzing the ACES (ALMA CMZ Exploration Survey) \h40 (99.02 GHz) recombination line and 99.6 GHz continuum emission data with synthesized beam widths of $2''.45$ (0.097 pc at 8.2 kpc) and $2''.14$, respectively. We apply the 'TeEM' method ($\Te$--$EM$ mapping), which creates $\Te$ and $EM$ maps from input 2D maps of the continuum and integrated line intensity. The analysis covers the entire ACES field from $l\sim -0^\circ.6$ to $+0^\circ.8$ and from $b\sim -0^\circ.2$ to $+0^\circ.1$. The area analyzed is complete and includes previously known HII regions such as Sgr B2, Sgr B1, the Sickle, the Pistol, thermal filaments (Bridges), Sgr A HII regions, the Minispiral, and many other known HII regions. Sgr C is not included in the analysis due to the insufficient signal-to-noise ratio in the recombination line map. The mean electron temperature over the CMZ is determined to be $\Tcmz= 5872 \pm 78 ~{\rm (SE)} ~\pm 3682~{\rm (SD)}$ K (SE:standard error of the mean, SD: pixel-to-pixel standard deviation). Some HII regions, such as Sgr B2 Main and the Minispiral, exhibit large scatter and an internal $\Te$ gradient of several thousand K per parsec. The $EM$ distribution is more diverse, varying by orders of magnitude from $\sim 10^5$ to $\sim 3\times 10^8$ \emunit within the CMZ, as well as within individual HII regions.
