2011.0.00022.SV
This README file contains a description of the Orion KL ALMA Band 1 Science Verification data, calibration, scripts, and data products.
Observations with the spectral scan mode covering the frequency range from 35.1 to 49.63 GHz at a spectral resolution of 244.172 kHz were carried out.
36-41 antennas (depending on the executions) are used for the observations, and the baseline lengths range from 15 to 500 m. The resolution achieved is 5.43 x 3.97 arcseconds in the spectral window at the lowest frequency centered at 35.57 GHz and 4.26 x 2.88 arcseconds in the spectral window at the highest frequency centered at 49.16 GHz
The RMS achieved is ~3 mJy in the continuum image of the spectral window at 35.57 GHz and is 1.8 mJy at 49.16 GHz. The RMS in the continuum images is limited by the dynamical range because of the presence of the strong extended emission. The RMS achieved in the line images ranges from 1 mJy at 35.1 GHz to 1.8 mJy at 49.6 GHz with a channel width of 244.172 kHz.
Additional information can be found in the comments section included in this README.
The Calibrated Data and Reference Images provided here were produced using CASA version 6.5.4.9 with the Pipeline version 2023.1.0.124.
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DATA CATEGORIES
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2011.0.00022.SV
`-- sg_ouss_id
`-- group_ouss_id
`-- member_ouss_id
|-- calibration Calibration tables
|-- log Casa logs
|-- product FITS products for science targets and calibrators made by pipeline.
Manual imaging of science targets for continuum is also included.
|-- qa Weblog of data calibration and imaging
|-- script Scripts
|-- raw Uncalibrated raw data that were used to make the final products.
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FILES
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Main science imaging products:
The symbol # means the spectral window ID of {23, 25, 27, 29}, {43, 45, 47, 49}, {63, 65, 67, 69} and {83, 85, 87, 89}.
Pipeline-products
product/*_sci*cont*pbcor.fits Primary beam corrected aggregate interferometric continuum images
product/*_sci*cube*pbcor.fits Primary beam corrected, continuum subtracted interferometric spectral line cubes
product/*spw#.mfs.*.fits Per-spectral window (SPW) "multifrequency synthesis" (=continuum) products
product/*.pb.fits Primary beam response
product/*.mask.fits Mask used in the imaging process
Manual imaging-products
product/*manual*tt0.pbcor.fits Primary beam corrected continuum images
product/*manual*.mask.fits Mask used in the imaging process
product/*manual*.pb.fits Primary beam response
Main quality reports:
qa/*.weblog.tgz Data calibration and imaging diagnostic tables and plots
Selected additional data products:
calibration/* Files needed for the restoring of the calibrated measurement set (MS)
log/*.casa_commands.log List of equivalent CASA commands for pipeline processed data
log/*.casa-*.log Processing log files if they are not included in the weblog
raw/*asdm.sdm.tar Uncalibrated raw data (download the data in a separate link)
script/*.scriptForPI.py Master script to generate the calibrated MS (recommended)
script/*.casa_piperestorescript.py Pipeline script to restore calibrated MS
script/*.casa_pipescript.py Script to tweak the pipeline parameters
script/scriptForContinuumImaging.py Script for manual continuum imaging
script/spw#_cont_chan.txt Lists of the channels used for continuum subtraction and imaging
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SUPPLEMENTS:
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OrionKL_Band1_UncalibratedData.tgz contains the raw data:
* uid___A002_X1168a11_X4eba.asdm.sdm
* uid___A002_X1168a11_X566b.tar.asdm.sdm
* uid___A002_X1168a11_Xe188.tar.asdm.sdm
* uid___A002_X1168a11_X15440.tar.asdm.sdm
OrionKL_Band1_CalibratedData_line.tgz contains the calibrated measurement sets (visibility) of the science target with continuum subtraction.
* uid___A002_X1168a11_X15440_targets_line.ms
* uid___A002_X1168a11_X4eba_targets_line.ms
* uid___A002_X1168a11_X566b_targets_line.ms
* uid___A002_X1168a11_Xe188_targets_line.ms
OrionKL_Band1_CalibratedData.tgz contains the calibrated measurement sets (visibility) of the science target without continuum subtraction.
* uid___A002_X1168a11_X4eba_targets.ms
* uid___A002_X1168a11_X15440_targets.ms
* uid___A002_X1168a11_X566b_targets.ms
* uid___A002_X1168a11_Xe188_targets.ms
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COMMENTS:
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+Observations
The observations were done in 4 different executions from 2024 April 26 to April 28. The PWV was 2-3 mm. 41 antennas are used for the first and second execution, 36 antennas for the third execution, and 40 antennas for the fourth execution. A few antennas were heavily flagged during calibration. Total on-source time for the target source was about 129 min.
+Calibration
Calibration was done using the ALMA Pipeline in a standard manner. Significant bandpass ripple is found in bandpass calibration. The amplitude of the ripple is about 1%. Similar ripples also impact the data of the target source. Because the amplitude of these ripples is low and lower than the noise of the science data, the ripple is not seen in the target source spectra per pixel. However, when integrating a sufficiently large area, the ripple with its amplitude comparable to the noise level could appear in the target source spectra.
+Continuum subtraction
The identification of continuum channels was done manually. We first used the findcont function of the CASA pipeline for preliminary continuum identification and generated continuum subtracted images. Then we extracted spectra from these continuum subtracted images, measured the noise level, and selected the channels with intensity within +/-1 sigma noise. These channels were adopted for the continuum subtraction and imaging in the later pipeline calibration. The continuum emission is strong and complex in the target region, and the observing bandwidth is wide with many line detections. Therefore, users are recommended to verify the result of the continuum subtraction and make any necessary adjustments for their needs.
+Imaging
The line image cubes were generated by the pipeline with automasking with the default values. The clean and automasking works well in most of the channels, except for a few channels with very strong (e.g., masers) or very extended line emission.
Due to the wide bandwidth, the primary beam and angular resolution vary significantly across the spectral windows. This impacts the accuracy of the continuum image aggregating all spectral windows generated by the pipeline. Users are recommended to regenerate aggregated continuum images based on their needs.
The continuum images per spectral window were generated by the pipeline with nterms=1 and without multi-scale clean. The performance of clean and automasking is limited in this pipeline continuum imaging process. Additional continuum images were generated manually with nterms=2 and multi-scale clean, and the image qualities and masking are improved. Both continuum images are included in this data release. Because the continuum emission is strong and complex in the target region, which complicates automasking, users may like to adjust the clean masks and generate continuum images matching their needs.
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HOW TO EXECUTE THE CALIBRATION SCRIPT AND OBTAIN THE CALIBRATED MS FILES FROM RAW DATA:
If you would like to run scriptForPI.py to restore the MS originally calibrated in the pipeline.
(1) Download the raw data (*.asdm.sdm.tar files). After untarring the raw data, the path will be ./raw under ./member_ouss_id.
(2) Change into the ./script subdirectory, and run casa --pipeline -c scriptForPI.py using CASA version 6.5.4.9 (or 6.5.4.X where X is arbitrary).
Or, in the CASA interface (with --pipeline), enter,
casa <1>: exefile(‘scriptForPI.py’)
The calibrated MS (the same as in the supplements) will be restored in ./calibrated.
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HOW TO EXECUTE THE MANUAL IMAGING SCRIPT:
(1) Put the pipeline calibrated ms files of the target (uid___A002_X1168a11_X15440_targets.ms, uid___A002_X1168a11_X4eba_targets.ms, uid___A002_X1168a11_X566b_targets.ms, and uid___A002_X1168a11_Xe188_targets.ms), the text files of the continuum channel lists (spw#_cont_chan.txt), and the imaging script in the same directory
(2) In CASA 6.5.4
casa <1>: execfile(‘scriptForContinuumImaging.py’)
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HOW TO TWEAK THE PIPELINE SCRIPT:
If you want to tweak the parameters of pipeline calibration, please refer to the ALMA Science Pipeline User’s Guide for details in,
https://almascience.eso.org/processing/alma_pipeline_user_s_guide_for_release_2024-1.pdf