70 $\mu$m红外暗团块早期恒星形成阶段的水脉泽探测
Water maser detections toward 70 $μ$m infrared dark clumps at early star formation stage
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中文总结 AI 辅助
本研究利用VLA在五个70微米红外暗团块中首次探测到水脉泽，揭示了早期恒星形成活动，并提供了脉泽性质及磁场上限等关键信息。
中文摘要 AI 辅助
水脉泽为恒星形成早期阶段的激波气体和原恒星活动提供了强有力的探针。利用甚大阵列（VLA）K波段对22 GHz水谱线的观测，我们首次在五个70 ${\mu}$m红外暗团块中的致密核探测到水脉泽，为早期演化阶段的活跃恒星形成提供了证据。我们探测到十个未分辨的脉泽斑点，包含十三个速度分量，峰值流量密度为13--499 mJy，去卷积后的半极大全宽（FWHM）为0.51--3.54 km s-1。其中十一个分量的FWHM低于1 km s-1，而它们相对于由NH3(1,1)主线示踪的系统速度的速度偏移范围为0.83至50.73 km s-1。四个水脉泽斑点与1.3 mm连续谱辐射相关联，其中三个还与CO 2-1发射示踪的分子外流相关联。在观测视场内，其余斑点未探测到CO外流特征，这表明水脉泽可能示踪了深度嵌入的原恒星活动，其外流在CO发射中尚不可探测。对于AGAL031，最强脉泽分量未探测到StokesV发射，这给出了视线方向磁场强度的上限，约为几百mG。我们的结果表明，恒星形成在70 ${\mu}$m红外暗团块中已经活跃，而22 GHz水脉泽为早期原恒星环境提供了见解，这些环境难以用常见的恒星形成示踪物探测。
英文摘要
Water masers provided powerful probes of shocked gas and protostellar activity during the early stages of star formation. Using VLA K-band observations of the 22 GHz water line, we report the first detections of water masers toward dense cores in five 70 $μ$m infrared dark clumps, providing evidence for active star formation at an early evolutionary stage. We detected ten unresolved maser spots comprising thirteen velocity components, with peak flux densities of 13--499 mJy and deconvolved full widths at half maximum (FWHMs) of 0.51--3.54 km s-1. Eleven components had FWHMs below 1 km s-1, while their velocity offsets from the systemic velocities traced by the NH3(1,1) main line ranged from 0.83 to 50.73 km s-1. Four water maser spots were associated with 1.3 mm continuum emission, three of which were also associated with molecular outflows traced by CO 2-1 emission. No CO outflow signature was detected toward the remaining spots within the observed field of view, suggesting that water masers could trace deeply embedded protostellar activity whose outflows were not yet detectable in CO emission. For AGAL031, the non-detection of StokesV emission toward the strongest maser component yields an upper limit on the line of sight magnetic field strength on the order of a few hundred mG. Our results showed that star formation was already active in 70 $μ$m infrared dark clumps and that 22 GHz water masers provided insights into early protostellar environments that remained difficult to probe with common star formation tracers.
发表机构
- Guangxi University（广西大学）
- Nanjing University（南京大学）
- Worcester State University（伍斯特州立大学）
- Center for Astrophysics—Harvard & Smithsonian（哈佛-史密森尼天体物理中心）
- Korea Astronomy and Space Science Institute（韩国天文与空间科学研究所）
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