High-frequency long-baseline experiments with the Atacama Large Millimeter/submillimeter Array were organized to test the high angular resolution imaging capabilities in the submillimeter wave regime using baselines up to 16 km. Four experiments were conducted, two Band 7 (289 GHz) and two Band 8 (405 GHz) observations. Phase correction using band-to-band (B2B) phase referencing was used with a phase calibrator only 0.7deg away observed in Band 3 (96 GHz) and Band 4 (135 GHz), respectively. In Band 8, we achieved the highest resolution of 14x11 mas. We compared the synthesis images of the target quasar using 20 and 60 s switching cycle times in the phase referencing. In Band 7, the atmosphere had good stability in phase rms ( 1 rad over 2 minutes), which led to a significantly reduced coherence when using the 60 s switching cycle time. One of our four experiments indicates that the residual phase rms error after phase referencing can be reduced to 0.16 rad at 289 GHz in using the 20 s switching cycle time. Such conditions would meet the phase correction requirement of image coherence of >70% in Band 10, assuming a similar phase calibrator separation angle, emphasizing the need for such B2B phase referencing observing at high frequencies.

中文翻译：

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ALMA 带间相位参考：长基线和高频成像能力

组织了阿塔卡马大型毫米/亚毫米阵列的高频长基线实验，以使用长达 16 公里的基线测试亚毫米波范围内的高角分辨率成像能力。进行了四次实验，两个频段 7 (289 GHz) 和两个频段 8 (405 GHz) 观测。使用带间 (B2B) 相位参考进行相位校正，并使用相位校准器，分别在频段 3 (96 GHz) 和频段 4 (135 GHz) 中观察到仅 0.7 度。在波段 8 中，我们实现了 14x11 mas 的最高分辨率。我们在相位参考中使用 20 秒和 60 秒的切换周期时间比较了目标类星体的合成图像。在波段 7 中，大气在相位均方根（1 rad 超过 2 分钟）方面具有良好的稳定性，这导致在使用 60 秒开关周期时间时相干性显着降低。我们的四个实验之一表明，在使用 20 s 开关周期时间时，相位参考后的残余相位均方根误差可以在 289 GHz 下降低到 0.16 rad。这样的条件将满足波段 10 中图像相干性 >70% 的相位校正要求，假设相位校准器分离角相似，强调需要在高频下进行此类 B2B 相位参考观测。