Atmospheric limitations for high-frequency ground-based VLBI
Dominic W. Pesce, Lindy Blackburn, Ryan Chaves, Sheperd S. Doeleman, Mark Freeman, Sara Issaoun, Michael D. Johnson, Greg Lindahl, Iniyan Natarajan, Scott N. Pa… 展开作者
Dominic W. Pesce, Lindy Blackburn, Ryan Chaves, Sheperd S. Doeleman, Mark Freeman, Sara Issaoun, Michael D. Johnson, Greg Lindahl, Iniyan Natarajan, Scott N. Paine, Daniel C. M. Palumbo, Freek Roelofs, Paul Tiede
备注：
29 pages, 12 figures, accepted for publication in ApJ
Very long baseline interferometry (VLBI) provides the highest-resolution images in astronomy. The sharpest resolution is nominally achieved at the highest frequencies, but as the observing frequency increases so too does the atmospheric contribution to the system noise, degrading the sensitivity of the array and hampering detection. In this paper, we explore the limits of high-frequency VLBI observations using ngehtsim, a new tool for generating realistic synthetic data. ngehtsim uses detailed historical atmospheric models to simulate observing conditions, and it employs heuristic visibility detection criteria that emulate single- and multi-frequency VLBI calibration strategies. We demonstrate the fidelity of ngehtsim's predictions using a comparison with existing 230 GHz data taken by the Event Horizon Telescope (EHT), and we simulate the expected performance of EHT observations at 345 GHz. Though the EHT achieves a nearly 100% detection rate at 230 GHz, our simulations indicate that it should expect substantially poorer performance at 345 GHz; in particular, observations of M87 at 345 GHz are predicted to achieve detection rates of $\lesssim$20% that may preclude imaging. Increasing the array sensitivity through wider bandwidths and/or longer integration times -- as enabled through, e.g., the simultaneous multi-frequency upgrades envisioned for the next-generation EHT -- can improve the 345 GHz prospects and yield detection levels that are comparable to those at 230 GHz. M87 and Sgr A* observations carried out in the atmospheric window around 460 GHz could expect to regularly achieve multiple detections on long baselines, but analogous observations at 690 and 875 GHz consistently obtain almost no detections at all.
Frequency Standard Contributions to Limitations on the Signal-to-Noise Ratio in Very Long Baseline Interferometric (VLBI) Observations
Jet Propulsion Laboratory, California Institute of Technology（加州理工学院喷气推进实验室）；Academia Sinica Institute of Astronomy and Astrophysics（中央研究院天文及天文物理研究所）；Blue Origin（蓝色起源）
Radboud University（拉德堡德大学）；SENER AEROESPACIAL（SENER航空航天公司）；GMV AD.（GMV AD.公司）；University of Würzburg（维尔茨堡大学）；Goethe Universität Frankfurt（法兰克福歌德大学）；Max-Planck-Institut für Radioastronomie（马克斯·普朗克射电天文研究所）；European Space Agency（欧洲空间局）；Serco Netherlands BV（塞尔科荷兰有限公司）；Scaleout Systems（Scaleout Systems公司）；Alén Space（阿伦航天公司）；German Aerospace Center (DLR)（德国航空航天中心）；Instituto de Astrofísica de Andalucía-CSIC（安达卢西亚天体物理学研究所）
Simulating an imaging atmospheric radio telescope to observe cosmic gamma rays and cosmic neutrinos
Max-Planck-Institute for Nuclear Physics（马普核物理研究所）；University of Heidelberg（海德堡大学）；Radboud University Nijmegen（奈梅亨拉德伯德大学）；Nationaal Instituut voor Kernfysica en Hoge Energie Fysica (NIKHEF)（荷兰核与高能物理国家研究所）
Characterization of the MUSE NFM PSF as a function of atmospheric conditions: TipTop calibration
European Southern Observatory (ESO)（欧洲南方天文台）；INAF – Osservatorio Astrofisico di Arcetri（意大利国家天体物理研究所阿切尔菲天文台）；Finnish Centre for Astronomy with ESO, (FINCA), University of Turku（图尔库大学芬兰ESO天文中心）；Tuorla Observatory, Department of Physics and Astronomy, University of Turku（图尔库大学图奥拉天文台）；Turku Collegium for Science, Medicine and Technology (TCSMT), University of Turku（图尔库大学图尔库科学技术学院）；DOTA, ONERA（法国航空航天发展局）
