English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

In 2017, an Atacama Large Millimeter/submillimeter Array (ALMA)high-frequency long baseline campaign was organized to test image capabilitieswith baselines up to 16 km at submillimeter (submm) wavelengths. Weinvestigated image qualities using ALMA receiver Bands 7, 8, 9, and 10 (285-875GHz) by adopting band-to-band (B2B) phase referencing in which a phasecalibrator is tracked at a lower frequency. For B2B phase referencing, it isexpected that a closer phase calibrator to a target can be used, comparing tostandard in-band phase referencing. In the first step, it is ensured that aninstrumental phase offset difference between low- and high-frequency Bands canbe removed using a differential gain calibration in which a phase calibrator iscertainly detected while frequency switching. In the next step, comparativeexperiments are arranged to investigate the image quality between B2B andin-band phase referencing with phase calibrators at various separation angles.In the final step, we conducted long baseline imaging tests for a quasar at 289GHz in Band 7 and 405 GHz in Band 8 and complex structure sources of HL Tau andVY CMa at ~670 GHz in Band 9. The B2B phase referencing was successfullyapplied, allowing us to achieve an angular resolution of 14x11 and 10x8 mas forHL Tau and VY CMa, respectively. There is a high probability of finding alow-frequency calibrator within 5.4 deg in B2B phase referencing, bright enoughto use an 8 s scan length combined with a 7.5 GHz bandwidth.

ALMA High-frequency Long Baseline Campaign in 2017: Band-to-band Phase Referencing in Submillimeter Waves