甲醛脉泽搜寻及辐射性质观测研究

In the Mikly Way, formaldehyde (H2CO) masers have only been detected in the 6 cm transition in ten sources. All of them are associated with massive star forming regions. There are so rare for the detected H2CO masers, making the search and study of them to be important for the whole molecular astronomical field. Recently the application of this project suggests that ionized jet/outflow environments might provide efficient pumping for the H2CO masers, with the ionized jet/outflow-driven shock causing collisional excitation, and are also able to provide additional seed photons for maser amplification of the radio continuum emission. Based on this argument, this proposed project will use the advanced radio single dish, interferometric array and VLBI equipments to carry out the following scientific researches: 1) systemic H2CO maser searchs towards larger- size sample sources associated with ionized jet/outflow environments; 2) long-term monitoring observations for investigating the variations of flux density of the H2CO masers; 3) VLBI polarization observations for the strong H2CO masers. Some of these observations are proposed for the first time. Through these observations, it can be expected to: 1) find much more H2CO masers, enriching the number of the known formaldehyde masers; 2) enhance the new knowledge for the excitation mechanism and the radiation characteristics of the H2CO masers, and obtain the relationships between the H2CO masers and the physical and kinematic environments of the star forming regions or evolved stars. All above researches will provide the most important observational evidences for understanding H2CO masers. In this project, we will find much more new and fast scientific discoveries in time.

在银河系内，甲醛分子脉泽辐射仅在10个恒星形成区中被探测到，数量之少，使得搜寻和研究它们对整个分子天文研究领域具有重要意义。本项目基于申请人近期提出的甲醛脉泽可能在电离喷流环境下激发的这一重要科学论据，依托国内外先进射电望远镜单天线、干涉阵及VLBI设备，开展具有电离喷流样本的甲醛脉泽搜寻，对甲醛脉泽流量监测，以及强甲醛脉泽的VLBI偏振观测等工作。其中部分观测计划尚属国际上首次提出。通过这些观测，预期将发现更多的甲醛脉泽源，增丰甲醛脉泽源数目，并为理解甲醛脉泽的激发机制、各种辐射特性、及它们与恒星形成区或主序后星星周物理环境及动力学关联性提供重要的观测证据。本项目及时地对由新选源标准建立样本（包括大、小质量恒星形成区及主序后星）开展甲醛脉泽搜寻工作，极有可能取得更多新的及快速的科学发现。

在银河系内，甲醛分子脉泽辐射仅在10个恒星形成区中被探测到，数量之少，使得搜寻和研究它们对整个分子天文研究领域具有重要意义。本项目依托国内外先进射电望远镜单天线、干涉阵等设备，开展具有电离喷流样本的甲醛脉泽搜寻及对甲醛脉泽流量监测等工作。本项目预期目标为：发现更多的甲醛脉泽源，增丰甲醛脉泽源数目，并为理解甲醛脉泽的激发机制、各种辐射特性、及它们与恒星形成区或主序后星星周物理环境及动力学关联性提供重要的观测证据。通过项目的执行，完成了课题主要研究目标及内容，包括：1）完成了各类样本的甲醛脉泽或吸收的搜寻观测，并发现了一颗新的甲醛脉泽源；2）完成对AGB阶段硅酸盐星的甲醛分子单天线观测，发现了它们具有双峰的甲醛谱轮廓特征；3）对发现的一颗新的甲醛脉泽源（G24.33+0.14）开展了多历元天马单天线流量监测及干涉阵的成图观测研究，并揭示甲醛脉泽可能与间歇吸积现象相关联； 4）对一颗具有甲醛吸收线的间歇吸积源（G358.93-0.03）开展了脉泽谱线的系统研究，其中发现了三种新分子脉泽，并提出这些新分子脉泽示踪了大质量恒星形成的漩涡吸积流和间歇吸积过程；5）在2颗吸积爆发源中探测到了异常丰富的甲醇及氨分子脉泽跃迁，并发现这些脉泽具有快速的光变，证实了该源中存在间歇吸积现象。这些研究成果为理解甲醛脉泽的产生所需的特殊物理条件以及它们与间歇吸积过程的关联性提供重要的观测依据。