电离氢区的恒星形成分子定律
The HII Regions' Molecular Law of Star Formation
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中文总结 AI 辅助
该研究结合多设备成像数据，在电离氢区100pc尺度发现恒星形成率与分子气体面密度的关系斜率约1.85，且不同红移的恒星形成系统构成单一序列，为恒星形成分子定律提供了新观测约束。
中文摘要 AI 辅助
我们结合哈勃空间望远镜（HST）、詹姆斯·韦布空间望远镜（JWST）以及地面毫米级设备的成像数据，在三个邻近星系NGC628、NGC5194和NGC5236的电离氢区（HII regions）约100pc尺度上，研究恒星形成率（SFR）与分子气体之间的关联。三个星系的JWST 21微米图为高分辨率下尘埃吸收的SFR提供了独特观测视角。我们发现，SFR面密度与分子气体面密度的对数-对数关系斜率约为1.85，该值显著大于以往邻近星系的研究结果，但与银河系分子云的趋势更为接近。这种陡峭的关系在更大的约500pc尺度上同样成立，其成因在于高分辨率成像可清晰分离恒星形成区的辐射与星系基底的弥散辐射。研究还发现，21微米的弥散辐射与星系恒星质量存在关联。与恒星形成物理模型的对比尚无定论：这些模型与100pc尺度数据的轨迹重叠，但难以复现数据的离散度；可能的例外是那些在气体密度概率分布中加入幂律尾部的模型，原因是这类模型允许大量自由参数。我们进一步发现，局域电离氢区、高红移恒星形成团块以及低、高红移星暴星系，在气体面密度跨越三个数量级的范围内构成了单一的恒星形成序列。
英文摘要
We combine imaging data from the HST, JWST, and ground-based millimeter facilities to investigate the correlation between star formation rate (SFR) and molecular gas at the ~100 pc scale of HII regions in three nearby galaxies: NGC628, NGC5194 and NGC5236. The JWST 21 micron maps of the three galaxies offer a unique insight into the dust-absorbed SFR at high resolution. We find that the relation between the surface densities of SFR and molecular gas has a slope of ~1.85, in log-log scale, significantly steeper than previous results for nearby galaxies but closer to the trends found for molecular clouds in the Milky Way. The steep relation also holds on larger, ~500 pc, scales, and results from the high-resolution imaging that cleanly isolates the star-forming region emission from the underlying galaxy's diffuse contribution. The diffuse emission at 21 micron is, in fact, found to correlate with the galaxy's stellar mass. Comparisons with physical models of star formation are inconclusive; they overlap with the locus of the 100 pc data, but have difficulties in reproducing the data scatter. Possible exceptions are models that add a power law tail to the gas density probability distribution, due to the large range of free parameters allowed. We find that local HII regions, high redshift star-forming clumps, and low and high redshift starburst galaxies form a single sequence of star formation over three orders of magnitude in gas surface density.
