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تسجيل مستخدم جديدALMA High-frequency Long Baseline Campaign in 2017: Band-to-band Phase Referencing in Submillimeter Waves
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In 2017, an Atacama Large Millimeter/submillimeter Array (ALMA) high-frequency long baseline campaign was organized to test image capabilities with baselines up to 16 km at submillimeter (submm) wavelengths. We investigated image qualities using ALMA receiver Bands 7, 8, 9, and 10 (285-875 GHz) by adopting band-to-band (B2B) phase referencing in which a phase calibrator is tracked at a lower frequency. For B2B phase referencing, it is expected that a closer phase calibrator to a target can be used, comparing to standard in-band phase referencing. In the first step, it is ensured that an instrumental phase offset difference between low- and high-frequency Bands can be removed using a differential gain calibration in which a phase calibrator is certainly detected while frequency switching. In the next step, comparative experiments are arranged to investigate the image quality between B2B and in-band phase referencing with phase calibrators at various separation angles. In the final step, we conducted long baseline imaging tests for a quasar at 289 GHz in Band 7 and 405 GHz in Band 8 and complex structure sources of HL Tau and VY CMa at ~670 GHz in Band 9. The B2B phase referencing was successfully applied, allowing us to achieve an angular resolution of 14x11 and 10x8 mas for HL Tau and VY CMa, respectively. There is a high probability of finding a low-frequency calibrator within 5.4 deg in B2B phase referencing, bright enough to use an 8 s scan length combined with a 7.5 GHz bandwidth.
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The Atacama Large millimeter/submillimeter Array (ALMA) obtains spatial resolutions of 15 to 5 milli-arcsecond (mas) at 275-950GHz (0.87-0.32mm) with 16km baselines. Calibration at higher-frequencies is challenging as ALMA sensitivity and quasar dens
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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
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