ALMA Renormalization Correction

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Applying renormalization corrections to data

ALMA observations of sources with strong line emission are affected by amplitude calibration issues caused by the ALMA normalization strategy, as described in the following Knowledgebase Articles: [1] and [2].

If a correction factor of more than 2% is calculated for a dataset, it will be corrected during data reduction for all newly observed datasets. If you have a dataset where this correction has not been applied (this should be indicated in the Pipeline weblog or Manual Data Reduction Script), the following example script will calculate and apply the corrections to the dataset:

__rethrow_casa_exceptions = True
    hifa_importdata(vis=[''], session=['session_1'], ocorr_mode='ca')
    hifa_renorm(apply=True, atm_auto_exclude=True) 

This script should be run in the calibrated/working/ directory after you've restored the calibrated data. The resulting uid*.ms file will be corrected if the renormalization factor is >2%. The calculated renormalization factors along with plots can be viewed in the weblog produced by the script. For more information, please refer to the Pipeline User's Guide. Please note that the hifa_renorm task is only available in CASA version 6.2.1-7 and Pipeline version 2021.2.0.128 and above. The parameter atm_auto_exclude is only available in CASA version with Pipeline version 2022.2.0.64 and above.