Probing the Milky Way Disk with Massive Stars

探索拥有大质量恒星的银河系盘

• 批准号: 1714688
• 负责人: Thomas Bania
• 金额: $ 45.31万
• 依托单位: Trustees of Boston University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-08-15 至 2023-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1714688&HistoricalAwards=false
• 关键词: Probing; Milky; Way; Disk; Massive

Galaxies live and die by their star formation. Galaxies, like our Milky Way, are rich in interstellar gas and dust clouds. Gravity causes some interstellar clouds to collapse and form stars. The largest, brightest, hottest, and most massive stars that form are called "OB stars." OB stars are seen at their birthplaces because in their short lifetimes they do not have time to move very far from the collapsing interstellar clouds from which they formed. The light from these OB stars is energetic enough to create "HII Regions." HII regions are hot bubbles of fully ionized gas that surround their parent OB stars. OB star formation and the HII regions that go with it are mostly confined to the spiral arms of galaxies. HII regions are tracers of Galactic spiral structure.Collaborations with Haystack Observatory and Green Bank Observatory (GBO) will bring the excitement of radio astronomy to Boston University undergraduates and provide mentors at the Physics Inspiring the Next Generation (PING) Summer Camp for 9th grade girls and boys held at Green Bank. PING is a collaboration between GBO and the National Society of Black Physicists.The OB star chemical abundances indicate the present state of the interstellar gas and reveal the elemental enrichment caused by the nuclear processing of many stellar generations. They thus provide unique and important tracers of billions of years of Galactic chemical evolution (GCE). The Southern HII Region Discovery Survey (SHRDS) will use the Australian Telescope Compact Array to find hundreds of heretofore unknown HII regions. The SHRDS extends the successful Green Bank Telescope and Arecibo HRDS projects to the Southern sky; nearly half of the Milky Way disk cannot be observed from the Northern Hemisphere. The SHRDS will improve the Galactic HII region census in the largest unexplored part of the Milky Way disk where the location of the spiral arms and the galactic bar is especially uncertain. It will give the first complete map of where massive stars are forming in the entire Milky Way disk. This map will allow a detailed analysis of the overall structure of OB-star formation sites in the Milky Way and how the physical properties of HII regions change across the disk.New Galactic HII regions are discovered by detecting radio recombination line (RRL) radiation from candidate HII region targets. These targets are identified by comparing infrared and radio continuum images from existing surveys of the sky. Comparing far-IR and radio continuum survey data leads to a list of some 2,000 candidate HII regions in the Galaxy. RRL spectroscopic confirmation is needed to prove that a candidate is an H II region and to give its velocity. The recombination lines give kinematic distances and electron temperatures for the nebulae. Together, these allow derivation of the properties of the ionizing stars and the heavy element abundances, the metallicities, of the HII region gas. A Galactic scale map of HII region metallicities can inform both GCE and the merger history of the Milky Way. This project will achieve an areal density of sources, distributed throughout the Galactic disk, that can show local zones of metal enrichment (or depletion). This would provide evidence for mergers, thus adding a new tool for the study of Galactic archaeology.

星系的生死取决于其恒星的形成。 星系，就像我们的银河系一样，富含星际气体和尘埃云。 重力导致一些星际云塌陷并形成恒星。 形成的最大、最亮、最热和质量最大的恒星被称为“OB星”。 OB型恒星在它们的诞生地被看到，因为在它们短暂的生命周期中，它们没有时间远离它们形成的坍缩星际云。 这些 OB 恒星发出的光能量足以形成“HII 区域”。 HII 区域是完全电离气体的热气泡，围绕着其母 OB 星。 OB 恒星的形成和与之相伴的 HII 区域大多局限于星系的旋臂。 HII 区域是银河系螺旋结构的示踪剂。与 Haystack 天文台和 Green Bank 天文台 (GBO) 的合作将为波士顿大学本科生带来射电天文学的乐趣，并为在 Green Bank 举办的 9 年级女孩和男孩的物理激励下一代 (PING) 夏令营提供导师。 PING 是 GBO 和美国黑人物理学家协会之间的合作项目。OB 星的化学丰度表明了星际气体的现状，并揭示了由许多恒星代的核处理引起的元素富集。 因此，它们为数十亿年的银河化学演化（GCE）提供了独特而重要的示踪剂。 南部 HII 区域发现调查 (SHRDS) 将使用澳大利亚望远镜紧凑阵列来发现数百个迄今为止未知的 HII 区域。 SHRDS 将成功的格林班克望远镜和阿雷西博 HRDS 项目扩展到南方天空；从北半球无法观测到近一半的银河系盘面。 SHRDS 将改进银河系 HII 区域的普查，该区域是银河系盘中最大的未探索部分，那里的旋臂和银河棒的位置尤其不确定。 它将给出第一个完整的地图，显示整个银河系盘中大质量恒星的形成位置。 这张图将允许详细分析银河系 OB 星形成地点的整体结构以及 HII 区域的物理特性如何在整个盘中变化。通过检测来自候选 HII 区域目标的射电复合线 (RRL) 辐射，发现了新的银河系 HII 区域。这些目标是通过比较现有天空勘测的红外和射电连续谱图像来识别的。 通过比较远红外和射电连续谱调查数据，得出了银河系中约 2,000 个候选 HII 区域的列表。 需要 RRL 光谱确认来证明候选区域是 H II 区域并给出其速度。 重组线给出了星云的运动距离和电子温度。 总之，这些可以推导电离恒星的特性以及 HII 区域气体的重元素丰度和金属丰度。 HII 区域金属丰度的银河比例图可以告知 GCE 和银河系的合并历史。 该项目将实现分布在整个银盘上的源面密度，可以显示局部金属富集（或耗尽）区域。 这将为合并提供证据，从而为银河考古学的研究增加一个新工具。

项目成果

Detecting HII Regions in the Outer Scutum-Centaurus Arm

检测外盾板-半人马臂中的 HII 区域

• 发表时间: 2021
• 期刊: American Astronomical Society meeting #237
• 作者: Johnson, A.;Armentrout, W.;Anderson, L.;Bania, T.;Balser, D.;Wenger, T.
• 通讯作者: Wenger, T.

The 3-Helium Problem

3-氦问题

• 发表时间: 2020
• 期刊: American Astronomical Society meeting #235
• 作者: Balser, D.;Bania, T.
• 通讯作者: Bania, T.

A Green Bank Telescope Survey of Large Galactic H ii Regions

• DOI: 10.3847/1538-4365/aa956a
• 发表时间: 2017-10
• 期刊: The Astrophysical Journal Supplement Series
• 作者: L. Anderson;W. Armentrout;M. Luisi;T. Bania;D. Balser;T. Wenger

The Southern H ii Region Discovery Survey. I. The Bright Catalog

南部 H ii 地区发现调查。

• DOI: 10.3847/1538-4365/aaf8ba
• 发表时间: 2019
• 期刊: The Astrophysical Journal Supplement Series
• 作者: Wenger, Trey V.;Dickey, John. M.;Jordan, C. H.;Balser, Dana S.;Armentrout, W. P.;Anderson, L. D.;Bania, T. M.;Dawson, J. R.;McClure-Griffiths, N. M.;Shea, Jeanine
• 通讯作者: Shea, Jeanine

HII Regions and the Warm Ionized Medium

HII 区域和暖电离介质

• 发表时间: 2019
• 期刊: Bulletin of the American Astronomical Society
• 作者: Anderson, Loren;Armentrout, William P.;Bania, Thomas M.;Balser, Dana S.;Luisi, Matteo;Wenger, Trey V.;Roshi, D. Anish
• 通讯作者: Roshi, D. Anish