[论文解读] The Next Generation Very Large Array

Di Francesco, James, Chalmers, Dean+18 more|arXiv (Cornell University)|Oct 21, 2019

Radio Astronomy Observations and Technology被引用 10

一句话总结

本白皮书提议加拿大以7%的参与度加入下一代甚大阵列（ngVLA），这是一项变革性射电天文台，旨在将当前VLA的灵敏度、分辨率和频率覆盖范围（1.2–115 GHz）提升一个数量级。ngVLA将通过其先进的阵列配置以及加拿大主导的天线、接收机和相关器技术，推动行星形成、天体化学、星系演化和黑洞研究等领域的突破性科学进展。

ABSTRACT

The next generation Very Large Array (ngVLA) is a transformational radio observatory being designed by the U.S. National Radio Astronomy Observatory (NRAO). It will provide order of magnitude improvements in sensitivity, resolution, and uv coverage over the current Jansky Very Large Array (VLA) at ~1.2-50 GHz and extend the frequency range up to 70-115 GHz. The ngVLA will consist of three arrays working in parallel: i) a Main Array of 214 x 18-m antennas clustered at the current VLA site but spread within and beyond New Mexico that will provide baselines of 0.01-1000 km; ii) a Short Baseline Array of 19 x 6-m antennas located at the Main Array centre (+ 4 MA antennas with total-power capabilities) for high sensitivity to low surface brightness emission, and; iii) a Long Baseline Array of 30 x 18-m antennas located across the U.S. from Hawaii to the Virgin Islands, as well as western Canada, for extremely high resolution imaging with a maximum ~8,800 km baseline. The ngVLA concept has been submitted for consideration to the U.S. Astro2020 decadal survey panel, and soon thereafter it will be submitted to the U.S. National Science Foundation’s Major Research Equipment and Facility Construction program. The goal is to have early science with ngVLA as early as 2028 and full operations by 2034.<br> <br> The ngVLA will be a PI-proposal driven observatory and will tackle a wide range of high-impact key science projects that shaped its overall design. For example, the ngVLA will probe the innermost “terrestrial” zones of nearby circumstellar disks for forming planets, search for interstellar signals from key prebiotic molecules such as simple amino acids, trace the evolution of gas within galaxies across cosmic time, plumb the Galactic Centre for pulsars that will test General Relativity in new regimes, and explore the growth and evolution of black holes within and beyond our Galaxy in the era of multi-messenger astronomy. The ngVLA’s versatile design will also enable many other fundamental advances, as detailed in the recently published, topically diverse ngVLA Science Book.<br> <br> NRAO is seeking international partnerships at the 25% level to build and operate the ngVLA. Since Canadians have been historically major users of the VLA and have been valued partners with NRAO for ALMA, our participation is welcome. Canadians have been actually involved in ngVLA discussions for the past five years, and have played leadership roles in the ngVLA Science and Technical Advisory Councils. Canadian technologies are also very attractive for the ngVLA, in particular our designs for radio antennas, receivers, correlators, and data archives, and our industrial capacities to realize them. Indeed, the Canadian designs for the ngVLA antennas and correlator/beamformer are presently the baseline models for the project. Five other countries have also expressed interest in participating in ngVLA.<br> <br> Given the size of Canada’s radio community and earlier use of the VLA (and ALMA), we recommend Canadian participation in the ngVLA at the 7% level. Such participation would be significant enough to allow Canadian leadership in ngVLA’s construction and usage. Canada’s participation in ngVLA should not preclude its participation in SKA; access to both facilities is necessary to meet Canada’s radio astronomy needs. Indeed, ngVLA will fill the gap between those radio frequencies observable with the SKA and ALMA at high sensitivities and resolutions. Canada’s partnership in ngVLA will make it a major player in global radio astronomy, with access to cutting-edge facilities together covering approximately three orders of magnitude in frequency.

研究动机与目标

• 倡导加拿大以7%的贡献水平参与ngVLA，以确保在建设与科学运行方面的领导地位。
• 突出加拿大在ngVLA科学和技术顾问委员会中的现有领导角色，以及其已验证的技术贡献。
• 将ngVLA定位为ALMA与SKA的重要补充，填补两者之间的频率空白，实现对高灵敏度、高分辨率观测的全面覆盖。
• 通过利用在天线设计、相关器和数据系统方面的专长，确保加拿大在射电天文学领域的全球领导地位。
• 通过培训、科普宣传和社区参与计划，支持ngVLA的公平、多元与包容性参与。

提出的方法

• 设计三阵列ngVLA系统：主阵列（214个18米天线）、短基线阵列（19个6米天线）和长基线阵列（30个18米天线），分布于北美各地。
• 利用光纤将所有天线的信号传输至新墨西哥州VLA站点的中央相关器。
• 采用加拿大设计的天线和相关器/波束成形器作为性能与成本建模的基准模型。
• 通过ngVLA科学与技术顾问委员会开展由社区主导的科学案例开发，包括ngVLA科学手册中的88个科学章节。
• 整合多历元观测与高动态范围成像技术，用于研究时变盘结构与低表面亮度特征。
• 利用现有的加拿大基础设施与工业能力，支持ngVLA的建设与运行，包括数据档案和接收机技术。

实验结果

研究问题

• RQ1 加拿大如何通过7%的参与水平实现ngVLA在科学与技术上的领导地位？
• RQ2 ngVLA增强的灵敏度与分辨率在探测原行星盘中类地行星带的行星形成方面将带来哪些科学突破？
• RQ3 ngVLA能否探测到行星形成盘中平面区域的星际前生命分子，如甘氨酸与丙氨酸？
• RQ4 ngVLA将如何与ALMA和SKA协同工作，覆盖三个数量级的频率范围，实现对射电天空的全面观测？
• RQ5 ngVLA研发过程中存在哪些项目管理、科学与技术风险？如何通过国际合作与成熟技术加以缓解？

主要发现

• ngVLA在125 pc距离下可实现约5毫角秒的分辨率，足以对邻近原行星盘中的类地行星带（1 AU量级）进行详细成像，仅需5小时积分即可探测到由行星引起的缝隙与环状结构。
• ngVLA将能够探测关键前生命分子（如氨）的雪线，并成为首个具备探测星际氨基酸（如甘氨酸与丙氨酸）信号能力的设施。
• ngVLA将能够解析从宇宙诞生一亿年内至今的星系气体动力学，实现对恒星形成与金属丰度演化的全程追踪。
• ngVLA将通过精确定位引力波事件的射电对应体，并研究银河系中心的脉冲星，推动多信使天文学的发展，用于检验广义相对论。
• 加拿大设计的天线与相关器已作为ngVLA性能与成本建模的基准模型，证实了加拿大在该项目中的技术领导地位。
• 7%的投入（建设阶段1.5亿美元，运行阶段650万美元/年）将确保加拿大获得对价值20亿美元的变革性设施的访问权，并持续保持其在射电天文硬件与科学领域的全球领先地位。