Collaborative Research: Star Formation Processes in Dwarf Galaxies

合作研究：矮星系中的恒星形成过程

• 批准号: 0204922
• 负责人: Deidre Hunter
• 金额: $ 37.5万
• 依托单位: Lowell Observatory
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-09-01 至 2006-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0204922&HistoricalAwards=false
• 关键词: Collaborative; Research; Star; Formation; Processes

AST 0204922HunterDwarf irregulars are the most common type of galaxy in the Universe. They evolve relatively slowly over time and chemically resemble the outer parts of present-day spirals and young galaxies seen at high redshift. They have no density waves and little shear. Some are very close to us, permitting the resolution of clusters and star-forming regions. As a result, dwarf irregulars are ideal laboratories for studies of star formation in a pristine environment. They are also useful for comparisons with spirals, leading to a better understanding of both.The goals of this project are to determine what regulates star formation in dwarf galaxies on a wide range of scales, and then to apply this knowledge to other galaxies. Why do star formation rates in normal dwarf galaxies span a factor of over 104, and why are young stars always limited to the inner galaxy regions, far inside the radial extent of other stars and gas? What governs how and where dense molecular clouds form? To address these questions, Dr. Deidre Hunter, at Lowell Observatory, and Dr. Bruce Elmegreen, at IBM, have observed 139 reasonably normal, non-interacting, nearby galaxies without spiral arms. The data include optical and near-infrared imagesthat allow the star formation to be determined over the lifetimes of these galaxies, atomic HI maps that show the raw cloud material and environment for cloud formation, and observations of the warm and cold molecular clouds that give birth to the stars themselves. Although a previous grant emphasized data collection and processing, these investigators have already analyzed the properties of the HII regions in the sample, including their sizes, pressures, luminosities, and locations. They studied the neutral interstellar structure in the LMC and combined all their data for a comprehensive study of NGC 2366. The results have led to a revision in the theoretical framework for star formation: global instabilities and threshold column densities for star formation are less important than local processes and conditions; the thermal equilibrium properties of the interstellar medium are as important as self-gravity; turbulence and phase changes generally structure the gas into cloud and intercloud media, yet global disturbances such as bars and interactions change this, producing anomalously massive bound clusters. The results have also enhanced our perspective on star formation processes in normal spiral galaxies by illustrating how the expansion of shells and the condensation of clouds becomes more severe at low shear. With this new award, the investigators will capitalize on their large, multi-wavelength survey to finish the project by addressing the "big-picture" questions posed above. They will find how star formation evolves over space and time in a dwarf galaxy; consider the special effects at galaxy edges; show how the star formation history relates to the gas structure and other conditions for cloud formation; determine the formation requirements for star forming regions of different sizes and densities; determine the porosity of the interstellar medium and its role in possible feedback; and determine the overall structure of the dwarfs. Many of these results will have applications to other galaxy types and to other epochs in the Universe. ***

AST 0204922Hunterdwarf不规则是宇宙中最常见的星系类型。随着时间的流逝，它们的发展相对较慢，并且化学类似于当今螺旋的外部和高红移处的年轻星系。他们没有密度波和小剪切。有些非常接近我们，允许分辨集群和形成星形区域。结果，矮人的不规则是在原始环境中研究恒星形成的理想实验室。它们对于与螺旋形的比较也很有用，可以更好地理解两者。该项目的目标是确定哪些在各种尺度上调节矮星系中的恒星形成，然后将这些知识应用于其他星系。为什么正常矮星系中的恒星形成速率超过104倍，为什么年轻的恒星总是局限于内部星系区域，距离其他恒星和气体的径向范围内？是什么控制着密集的分子云的形成方式和位置？为了解决这些问题，洛厄尔天文台的Deidre Hunter博士和IBM的Bruce Elmegreen博士观察到了139个合理正常的，无相互作用的，附近没有螺旋臂的星系。数据包括光学和近红外影像图，可以在这些星系的一生中确定恒星形成，原子HI地图显示了云形成的原始云材料和环境，以及观察到恒星本身的温暖和冷分子云。尽管以前的赠款强调了数据收集和处理，但这些研究者已经分析了样本中HII区域的特性，包括它们的尺寸，压力，发光度和位置。他们研究了LMC中的中性星际结构，并将其所有数据结合在一起，以进行NGC 2366的全面研究。结果导致了恒星形成的理论框架的修订：全球不稳定性和恒星形成阈值柱密度不如本地过程和条件重要；星际培养基的热平衡特性与自我重度一样重要。湍流和相变通常将气体结构到云中和云间培养基中，但是诸如条形和相互作用之类的全球干扰会改变这一点，从而产生异常的大量结合簇。结果还通过说明壳的膨胀和云的凝结如何在低剪切时变得更加严重，从而增强了我们对正常螺旋星系中恒星形成过程的看法。 有了这个新奖项，调查人员将利用他们的大型多波长调查来完成该项目，以解决上面提出的“大型图片”问题。他们会发现矮人星系中的恒星形成如何在时空上演变。考虑星系边缘的特殊效果；展示恒星形成历史与气体结构和其他云形成条件的关系；确定不同尺寸和密度的恒星形成区域的形成要求；确定星际培养基的孔隙率及其在可能的反馈中的作用；并确定矮人的整体结构。其中许多结果将应用于其他星系类型和宇宙中的其他时期。 ***