Collaborative Research: Building an Event Horizon Telescope: (Sub)millimeter VLBI from the South Pole Telescope

目前一个非常感兴趣的研究课题是现在已知存在于我们银河系中心的大约400万太阳质量的超大质量黑洞。 类似的物体在其他星系中很常见。 关于银河系的奇异物体的大部分知识来自于对受其强大引力场影响的恒星运动学的研究。 到目前为止，还不存在直接对黑洞成像的可能性，或者更严格地说，它的事件视界，即引力“不归点”，在那里没有粒子或光子可以逃离黑洞。 银河系中心区域距离我们很远，大约8千秒差距，这使得我们很难通过任何直接的技术获得超大质量黑洞的高空间分辨率图像。 如果能够获得这样的图像，它们将是此类图像中的第一个，并且可以揭示关于黑洞和星系核心动力学的尚未想象的信息。为了解决这个具有挑战性的科学问题，D。亚利桑那大学的Marrone，S。东北射电天文台公司的Doeleman和芝加哥大学的J. Carlstrom打算增强现有的射电望远镜阵列，这些望远镜在最高的无线电频率（亚毫米，波长略短于1毫米）下工作，并在一种模式下工作，即由大陆基线隔开的望远镜相干地联合收割机组合它们的数据，以实现前所未有的空间分辨率。 一般的技术被称为甚长基线干涉测量术（VLBI），而使用的特定射电望远镜阵列被称为事件视界望远镜（EHT），部分是通过NSF以前的奖励开发的。 通过一项新的NSF提案，研究人员计划将南极望远镜（SPT）作为EHT的一个新站。 以这种方式增加台站（望远镜）可提高对无线电信号的灵敏度，并改善作为成像设备的仪器的空间响应，从而可对较暗的物体绘制质量更好的地图。 除了增加一个关键的观测站外，该技术还将采用一个新的、灵敏的双波段毫米波VLBI接收机，该接收机将采用国家射电天文台（NRAO）为阿塔卡马大型毫米波阵列（阿尔马）项目开发的超导混频器技术，并针对该项目的需要进行优化。 最后，经过验证的230 GHz设计将适用于345 GHz。NSF天文科学部通过其先进技术和仪器计划为这项工作提供资金。

A research topic of great current interest is the supermassive black hole of about 4 million solar masses that is now known to exist at the center of our Milky Way galaxy. Similar objects are common in other galaxies. Most of what is known about the Milky Way's exotic object comes from studies of the kinematics of stars influenced by its strong gravitational field. No possibility has heretofore existed for directly imaging the black hole, or more technically its event horizon, the gravitational "point of no return" from within which no particle or photon can escape the black hole. The galactic center region is distant, about 8 kpc, making it extraordinarily difficult to obtain high-spatial-resolution images of the supermassive black hole by any direct technique. If such images could be obtained, they would be the very first of their kind, and could reveal information not yet imagined about black holes and the dynamics in the cores of galaxies. To attack this challenging scientific problem, Drs. D. Marrone of the University of Arizona, S. Doeleman of the Northeast Radio Observatory Corporation, and J. Carlstrom of the University of Chicago intend to enhance an existing array of radio telescopes operating at the very highest radio frequencies (the submillimeter, with wavelengths somewhat shorter than a millimeter) and in a mode where telescopes separated by continental baselines coherently combine their data to achieve unprecedented spatial resolution. The general technique is termed Very Long Baseline Interferometry, or VLBI, and the particular array of radio telescopes to be used is referred to as the Event Horizon Telescope (EHT), developed in part through a previous award from NSF. Through a new NSF proposal the researchers plan to add the South Pole Telescope (SPT) as a new station to the EHT. Adding stations (telescopes) in this manner enhances sensitivity to radio signals and also improves the spatial response of the instrument as an imaging device, so that better-quality maps may be made of fainter objects. In addition to the addition of a key observing station, the technology will feature a new, sensitive dual-band millimeter-wave VLBI receiver, optimized for the needs of this project, that will employ superconducting mixer technology developed for the Atacama Large Millimeter Array (ALMA) project by the National Radio Astronomy Observatory (NRAO). Finally, the proven 230 GHz design will be adapted for use at 345 GHz.Funding for this work is being provided by NSF's Division of Astronomical Sciences through its Advanced Technologies and Instrumentation program.