Infrared Dark Clouds

红外暗云是大质量恒星和星团的诞生地。詹姆斯·杰克逊博士(波士顿大学)和他的团队将分析厘米、毫米、亚毫米和红外波长的一大套观测，并补充甚大望远镜、澳大利亚国家设施22米望远镜、高原德布雷和米利梅特里克射电天文研究所30米望远镜的新观测，以探索高质量原恒星演化中鲜为人知的过程。在这一资助期间，该团队将完成六个关键的科学项目：(1)测量约100颗大质量原恒星的光谱能量分布，从而测量辐射光度，(2)寻找高质量的“恒星前”核心，(3)通过搜索大质量恒星周围的星盘来测试“竞争吸积”的假设，(4)测试年轻的O星实际上以B星的形式进入主序，然后在它们成为主序O星的过程中继续吸收物质的想法，(5)测量大质量恒星形成云中的团质量函数。(6)研究大质量原恒星核的化学演化。当这个项目完成后，该团队将为理解大质量恒星形成早期阶段鲜为人知的过程做出重大贡献，并将测试两个关键的理论观点：“竞争吸积”和O星作为吸积B星首先进入主序的想法。杰克逊的团队在识别和描述红外暗云(IRDC)方面走在了前列。它们的特征大小(~几个分秒)和质量(~1000个太阳质量)类似于猎户座和蛇夫座中形成星团的分子团。然而，它们的低温表明它们处于较早的进化状态。对毫米/亚毫米尘埃连续体的成像显示，IRDC含有致密的核心，其大小(0.5秒)和质量(约100个太阳质量)与与大质量原恒星有关的“热核心”相匹配。对这些核心的研究表明，大约三分之一的核心含有恒星形成的明确证据。嵌入在几个IRDC核心中的原恒星的大测热光度表明，它们目前正在形成大质量恒星。干涉测量观测显示，这些大质量恒星伴随着一些质量较低的原恒星。因此，所有的初步证据都表明，IRDC是大质量恒星和星团形成的最早阶段。除了将在该奖项下开展的研究外，该提案还将资助两名女研究生和一名女博士后的培训和教育。此外，波士顿大学天文学系已与历史上的黑人大学菲斯克大学和范德比尔特大学达成合作协议，参加菲斯克-范德比尔特硕士-博士桥项目，该项目允许菲斯克学生在菲斯克攻读硕士学位，并保证被范德比尔特大学和波士顿大学的博士项目录取。

Infrared Dark Clouds are the birthplaces of both high-mass stars and star clusters. Dr. James Jackson (Boston University) and his team will analyze a large suite of observations at centimeter, millimeter, sub-millimeter, and infrared wavelengths, supplemented by new observations at the Very Large Telescope, the Australian Telescope National Facility 22-m telescope, Plateau de Bure, and Institut de Radio Astronomie Millimétrique 30-m telescopes to explore the poorly understood processes at play in high-mass protostellar evolution. The team will complete six key science projects in this funding period: (1) Measuring the spectral energy distributions, and hence, bolometric luminosities, of ~100 high-mass protostars, (2) Searching for high-mass "pre-stellar" cores, (3) Testing the suggestion of "competitive accretion" by searching for circumstellar disks surrounding high mass stars, (4) Testing the idea that young O stars actually enter the main-sequence as B stars and then continue to accrete material on their way to becoming main-sequence O stars, (5) Measuring the clump mass function in high-mass star forming clouds, and (6) Studying the chemical evolution of high-mass protostellar cores. When this project is complete, the team will have made a significant contribution to the understanding of the poorly-known processes at play in the earliest stages of high-mass star formation and will have also tested two key theoretical ideas: "competitive accretion" and the idea that O stars first enter the main-sequence as accreting B stars.Dr. Jackson's group has led the way in identifying and characterizing Infrared Dark Clouds (IRDCs). Their characteristic sizes (~few parsecs) and masses (~few 1,000 solar-masses) resemble those of cluster-forming molecular clumps such as those in Orion and Ophichus. Their cold temperatures, however, suggest that they are in an earlier evolutionary state. Imaging of the mm/sub-mm dust continuum reveals that IRDCs contain compact cores, whose sizes (0.5 parsecs) and masses (~100 solar masses) match those of "hot cores" associated with high-mass protostars. An examination of these cores reveals that about 1/3 contain unambiguous evidence of star formation. The large bolometric luminosities of the embedded protostars within several IRDC cores show that they are currently forming high-mass stars. Interferometric observations reveal that these high-mass stars are accompanied by a number of lower mass protostars. All of the initial evidence, therefore, suggests that IRDCs host the earliest stages of the formation of high-mass stars and star clusters. In addition to the research that will be carried out under this award, this proposal will fund the training and education of two female graduate students and one female post-doctoral student. Moreover, the Boston University Astronomy Department has entered into a collaborative agreement with Fisk University, a historically black college, and Vanderbilt University to participate in the Fisk-Vanderbilt Masters-Ph.D. Bridge Program which allows Fisk students to pursue their Master's degrees at Fisk with guaranteed admission into Ph.D. programs at Vanderbilt and Boston University.