Difference between revisions of "Karl G. Jansky VLA Tutorials"

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** [[Data flagging with viewer | Data flagging with '''viewer''']]
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Disclaimer: These tutorials provide guidelines to help users become familiar with VLA data reduction in [https://casa.nrao.edu/ CASA].  They offer examples for common general-use cases such as spectral line, continuum, linear polarization, and mosaicking.  However, the results demonstrated here are specific to the given data sets. The VLA is an extremely flexible instrument, and the techniques presented here may not apply equally to every individual VLA data set, especially if the type of observations, quality of data, or imaging analysis are particularly different or complicated. More details about CASA and its tasks and tools are available in the [https://casa.nrao.edu/casadocs Online CASA Documentation]. Further assistance with VLA data reduction is available through the [https://help.nrao.edu/ NRAO HelpDesk].
** [[Data flagging with plotms | Data flagging with '''plotms''']]
+
 
* [[Calibrating an EVLA OSRO HI data set]]
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''For data reduction of pre-EVLA upgrade VLA data, we provide separate, [https://casaguides.nrao.edu/index.php/Pre-upgrade_VLA_Tutorials pre-upgrade VLA data reduction tutorials]''
 +
 
 +
''In addition to the current VLA CASA Guides below, we also provide links to [https://casaguides.nrao.edu/index.php/Karl_G._Jansky_VLA_Tutorials-archived older versions of the VLA CASA guides].''
 +
 
 +
 
 +
== Introduction ==
 +
 
 +
The Karl G. Jansky Very Large Array (VLA) Tutorials are meant to guide the observer through some common types of data analysis, using example datasets, and including explanations of the individual steps. These analyses will be broadly applicable to many VLA data sets.
 +
 
 +
 
 +
If you are new to CASA, you may start with <h3>[https://casaguides.nrao.edu/index.php?title=Getting_Started_in_CASA Getting Started in CASA]</h3>
 +
 
 +
<!--
 +
If you are new to VLA Data, you may start with <h3>[[VLA: Getting Started | Getting Started with VLA data]]</h3>
 +
-->
 +
 
 +
 
 +
 
 +
== VLA Data Reduction Tutorials ==
 +
 
 +
 
 +
 
 +
=== High frequency (36GHz), spectral line data reduction: Carbon Star IRC+10216  ===
 +
<blockquote>
 +
* [http://casaguides.nrao.edu/index.php?title=VLA_high_frequency_Spectral_Line_tutorial_-_IRC%2B10216 IRC+10216 Tutorial] (CASA 5.5.0) 
 +
 
 +
* This tutorial requires to download a dataset <font color=green>1.1GB</font> in size
 +
 
 +
Calibrate and make image cubes of the line emission from this asymptotic giant branch star. This is a high-frequency VLA dataset.  Includes:
 +
* Inspecting data; basic flagging & calibration
 +
* Subtracting continuum emission
 +
* Imaging the spectral lines
 +
* Imaging the continuum
 +
* Image analysis
 +
* Self-calibration
 +
</blockquote>
 +
 
 +
=== 6cm Continuum Imaging, Mosaicking: Supernova Remnant 3C391 ===
 +
<blockquote>
 +
* [http://casaguides.nrao.edu/index.php?title=VLA_Continuum_Tutorial_3C391 3C391 Tutorial] (CASA 5.5.0)
 +
 
 +
* This tutorial requires to download a dataset <font color=orange>3.1GB</font> in size
 +
 
 +
Calibrate VLA continuum data, image a mosaic of the region in Stokes I.  Includes:
 +
* Inspecting data; basic flagging
 +
* Calibration
 +
* Image Analysis
 +
* Self-calibration
 +
</blockquote>
 +
 
 +
=== Polarization Calibration based on CASA pipeline standard reduction: The radio galaxy 3C75 ===
 +
<blockquote>
 +
* [https://casaguides.nrao.edu/index.php/Polarization_Calibration_based_on_CASA_pipeline_standard_reduction:_The_radio_galaxy_3C75 Polarization Calibration based on CASA pipeline (3C75)] (CASA 5.4.2)
 +
 
 +
* This tutorial requires to download a dataset <font color=red>10GB</font> in size
 +
 
 +
This tutorial demonstrates continuum calibration with the standard VLA pipeline and focuses on linear polarization calibration based on pipeline products, as well as full Stokes wide-field imaging and analysis. It includes:
 +
* Instructions on how to execute the VLA pipeline
 +
* How to modify pipeline products for polarization calibration
 +
* Linear Polarization Calibration
 +
* Wide-field Polarization Imaging
 +
* Self-calibration
 +
* Analysis of Polarization Products
 +
</blockquote>
 +
 
 +
=== P-band continuum imaging data reduction tutorial: 3C129  ===
 +
<blockquote>
 +
* [https://casaguides.nrao.edu/index.php/VLA_Radio_galaxy_3C_129:_P-band_continuum_tutorial 3C129 P-band Tutorial] (CASA 5.5.0)
 +
 
 +
* This tutorial requires to download a dataset <font color=red>26GB</font> in size
 +
 
 +
This low frequency VLA tutorial for the observation of radio galaxy 3C 129 focuses on low frequency wide-fractional-bandwidth data in the sub GHz regime and demonstrates multi-frequency synthesis imaging with w-projection.  This includes:
 +
* Basic flagging and evaluation
 +
* Automatic RFI Excision
 +
* Ionospheric Calibration
 +
* Self - Calibration
 +
* Widefield imaging
 +
</blockquote>
 +
 
 +
=== P-band spectroscopy tutorial: HI 21cm absorption in MG0414+0534 at z=2.64 ===
 +
<blockquote>
 +
* [https://casaguides.nrao.edu/index.php/MG0414+0534_P-band_Spectral_Line_Tutorial MG0414+0534 P-band Spectral Line Tutorial] (CASA 5.5.0)
 +
 
 +
* This tutorial is based on an archival data-set of 142 Gb in size, but we will extract only a <font color=red>15GB</font> portion of this data-set to work on.
 +
 
 +
This VLA P-band tutorial is aimed at calibrating and making an image cube of line-emission centered on 390.6 MHz. It includes:
 +
* P-band spectral-line observing strategies
 +
* Basic flagging options
 +
* Low-frequency calibration and self-calibration
 +
* Spectral-line imaging
 +
</blockquote>
 +
 
 +
== VLA Topical Guides ==
 +
 
 +
 
 +
=== Flagging VLA Data in CASA === 
 +
 
 +
<blockquote>
 +
* [http://casaguides.nrao.edu/index.php/VLA_CASA_Flagging Topical Guide: Flagging VLA Data] (CASA 5.5.0)
 +
 
 +
* This tutorial requires to download a dataset <font color=green>4.9GB</font> in size
 +
 
 +
This tutorial describes different flagging techniques, including:
 +
 
 +
* Identifying Problematic Antennas from the Operator Logs
 +
* Online Flags
 +
* Shadowing, zeroes, quacking, flagmanager, Hanning smoothing
 +
* Automatic RFI excision (TFCrop, RFlag)
 +
* Interactive Flagging (plotms, msview)
 +
* Flagging Summary & Report
 +
</blockquote>
 +
 
 +
=== Imaging VLA Data in CASA ===
 +
 
 +
<blockquote>
 +
* [http://casaguides.nrao.edu/index.php/VLA_CASA_Imaging Topical Guide: Imaging VLA Data] (CASA 5.5.0)
 +
 
 +
* This tutorial requires to download a dataset <font color=green>1.2GB</font> in size
 +
 
 +
The Imaging topical guide shows annotated examples of different imaging techniques that are applicable to different science applications. This tutorial includes:
 +
 
 +
* An Introduction to the CLEAN algorithm, data and imaging weights, primary and synthesized beams
 +
* Clean Output Images
 +
* Dirty Image, Regular CLEAN & RMS Noise, CLEAN with different Weights
 +
* Multi-Scale CLEAN
 +
* Multi-Scale, Wide-Field CLEAN (w-projection)
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* Multi-Scale, Multi-Term Frequency Synthesis
 +
* Multi-Scale, Multi-Term Frequency, Widefield CLEAN
 +
* Imaging Outlier Fields
 +
* Primary Beam Correction
 +
* Imaging Spectral Cubes, Beam per Plane
 +
* Image Header, Image Conversion
 +
</blockquote>
 +
 
 +
=== VLA Multi-Configuration Data Combination ===
 +
 
 +
<blockquote>
 +
* [http://casaguides.nrao.edu/index.php/VLA_Data_Combination Topical Guide: VLA Data Combination Guide] (CASA 5.5.0)
 +
* This tutorial requires to download a dataset <font color=green>1.4GB</font> in size
 +
 
 +
The VLA Data Combination Tutorial provides guidance on the combination of multi-configuration VLA data sets (in this case VLA A, B and C configurations). The data are re-weighted in two different ways, combined, and imaged. The guide also explains how to remove a time variable source from the data before combination.
 +
</blockquote>
 +
 
 +
=== Correcting for a Spectral Index in Bandpass Calibration ===
 +
 
 +
<blockquote>
 +
* [http://casaguides.nrao.edu/index.php/VLA_CASA_Bandpass_Slope Topical Guide: Correcting for a Spectral Index in Bandpass Calibration] (CASA 5.5.0)
 +
* This tutorial requires to download a dataset <font color=green>3.4GB</font> in size
 +
 
 +
This tutorial explains how to obtain a bandpass solution when the bandpass calibrator is a source with an unknown spectral index. This is typically encountered at high frequency observations, where the standard VLA flux density calibrators are too weak for high signal-to-noise bandpass solutions.
 +
</blockquote>
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 +
 
 +
 
 +
<!--
 +
==  VLA Tutorials for more Advanced Users ==
 +
 
 +
* '''Supernova SN2010FZ: Wide-band, narrow-field imaging; C-band (5-7 GHz)''' (CASA 4.4)
 +
<blockquote>
 +
* [http://casaguides.nrao.edu/index.php?title=EVLA_6cmWideband_Tutorial_SN2010FZ Supernova SN2010FZ Tutorial ]
 +
 
 +
* This tutorial requires to download a dataset <font color=orange>2.9GB</font> in size
 +
</blockquote>
 +
 
 +
<blockquote>
 +
Calibrate and image a galaxy field for this mid-frequency VLA observation.  This includes:
 +
* Excising RFI from the data
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* Basic flagging and calibration steps
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* Imaging from one spectral window to full dataset
 +
* Using multi-scale, multi-frequency synthesis
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* Image analysis
 +
</blockquote>
 +
 
 +
* '''Protostar G192.16-3.84: Wide-band, narrow-field imaging using 3-bit sampled data; Ka-band (27-38 GHz)''' (CASA 4.4)
 +
<blockquote>
 +
* [http://casaguides.nrao.edu/index.php?title=EVLA_3-bit_Tutorial_G192 Protostar G192.16-3.84 Tutorial]
 +
 
 +
* This tutorial requires the download of an <font color=red>18GB</font> dataset
 +
</blockquote>
 +
 
 +
<blockquote>
 +
Calibrate and image a protostar for this high-frequency VLA observation taken using the 3-bit samplers.  Note that this tutorial can be used as a guide for 8-bit data as well.  This includes:
 +
* Deleting bad data and RFI
 +
* Basic calibration, including tropospheric opacity and requantizer gain corrections
 +
* Bootstrapping to determine the spectrum of the bandpass calibration source
 +
* Imaging from a single spectral window to the full dataset
 +
* Using multi-frequency synthesis imaging
 +
* Image analysis
 +
</blockquote>
 +
 
 +
* '''Supernova G55.7_3.4: Wide-band, wide-field imaging; L-band (1-2 GHz)''' (CASA 4.4)
 +
<blockquote>
 +
* [http://casaguides.nrao.edu/index.php?title=EVLA_Wide-Band_Wide-Field_Imaging:_G55.7_3.4 G55.7+3.4 Tutorial]
 +
 
 +
* This tutorial requires to download a dataset <font color=red>14GB</font> in size
 +
</blockquote>
 +
 
 +
<blockquote>
 +
This low-frequency VLA tutorial for the observation of a supernova remnant focuses on RFI excision as well as imaging wide-field and wide-fractional-bandwidth data.  This includes:
 +
* Basic flagging and evaluation
 +
* Different methods for automatic RFI excision
 +
* Calibrating the data
 +
* Exploring different imaging options: widefield, multi-scale, and multi-frequency synthesis
 +
</blockquote>
 +
 
 +
 
 +
<!--
 +
== Specific Topics ==
 +
 
 +
 
 +
* [http://casaguides.nrao.edu/index.php?title=WorkshopSelfcal_(Caltech) Self-calibration]
 +
 
 +
 
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* CASA: [http://casaguides.nrao.edu/index.php?title=Writing_a_CASA_Task Writing a CASA task]
 +
 
 +
<blockquote>
 +
Presents the basics of writing a CASA task, and provides examples of tasks that will be helpful and instructive. 
 +
</blockquote>
 +
 
 +
* [[Baseband Stitching-CASA4.1]]
 +
 
 +
<blockquote>
 +
Demonstrates the use of the contributed "stitch" task to edit data which has been obtained in an overlapping subband mode.
 +
</blockquote>
 +
 
 
* [[Imaging Flanking Fields]]
 
* [[Imaging Flanking Fields]]
 +
 +
* [[Transient reduction pipeline]]
 +
 +
* [[Obtaining EVLA Data: 3C 391 Example]]
 +
 +
 +
== Other ==
 +
* Data Calibration, Imaging, and Analysis - simplified for Community Day Events: [[EVLA high frequency Spectral Line Tutorial - CDE]]
 +
-->
 +
 +
== VLA CASA Simulation Guide ==
 +
 +
<blockquote>
 +
* [https://casaguides.nrao.edu/index.php/Protoplanetary_Disk_Simulation_-_VLA VLA Protoplanetary Disk Simulation Guide] (CASA 5.5.0)
 +
* This tutorial does not require any download.
 +
 +
The VLA Protoplanetary Disk Simulation Guide shows examples on how to simulate VLA data based on model images. The tutorial will explain the main simulation tools, apply different parameters to simulations, and compares the results to the VLA exposure calculator.
 +
</blockquote>
 +
 +
== VLA CASA Pipeline Guide ==
 +
 +
<blockquote>
 +
* [http://casaguides.nrao.edu/index.php/VLA_CASA_Pipeline VLA CASA Pipeline Guide] (CASA 5.6.2)
 +
* This tutorial does not require any download.
 +
 +
The VLA CASA Pipeline Guide provides an example of a  VLA CASA pipeline run. Whereas the [https://science.nrao.edu/facilities/vla/data-processing/pipeline VLA Pipeline Web Page] describes the pipeline structure, requirements, execution options including restoration, pipeline output products, and pipeline modifications, this CASA guide is a detailed walkthrough of the weblog and provides interpretations of pipeline plots, tables, and Quality Assurance (QA) metrics.
 +
</blockquote>

Latest revision as of 17:40, 25 November 2019

Disclaimer: These tutorials provide guidelines to help users become familiar with VLA data reduction in CASA. They offer examples for common general-use cases such as spectral line, continuum, linear polarization, and mosaicking. However, the results demonstrated here are specific to the given data sets. The VLA is an extremely flexible instrument, and the techniques presented here may not apply equally to every individual VLA data set, especially if the type of observations, quality of data, or imaging analysis are particularly different or complicated. More details about CASA and its tasks and tools are available in the Online CASA Documentation. Further assistance with VLA data reduction is available through the NRAO HelpDesk.

For data reduction of pre-EVLA upgrade VLA data, we provide separate, pre-upgrade VLA data reduction tutorials

In addition to the current VLA CASA Guides below, we also provide links to older versions of the VLA CASA guides.


Introduction

The Karl G. Jansky Very Large Array (VLA) Tutorials are meant to guide the observer through some common types of data analysis, using example datasets, and including explanations of the individual steps. These analyses will be broadly applicable to many VLA data sets.


If you are new to CASA, you may start with

Getting Started in CASA



VLA Data Reduction Tutorials

High frequency (36GHz), spectral line data reduction: Carbon Star IRC+10216

  • This tutorial requires to download a dataset 1.1GB in size

Calibrate and make image cubes of the line emission from this asymptotic giant branch star. This is a high-frequency VLA dataset. Includes:

  • Inspecting data; basic flagging & calibration
  • Subtracting continuum emission
  • Imaging the spectral lines
  • Imaging the continuum
  • Image analysis
  • Self-calibration

6cm Continuum Imaging, Mosaicking: Supernova Remnant 3C391

  • This tutorial requires to download a dataset 3.1GB in size

Calibrate VLA continuum data, image a mosaic of the region in Stokes I. Includes:

  • Inspecting data; basic flagging
  • Calibration
  • Image Analysis
  • Self-calibration

Polarization Calibration based on CASA pipeline standard reduction: The radio galaxy 3C75

  • This tutorial requires to download a dataset 10GB in size

This tutorial demonstrates continuum calibration with the standard VLA pipeline and focuses on linear polarization calibration based on pipeline products, as well as full Stokes wide-field imaging and analysis. It includes:

  • Instructions on how to execute the VLA pipeline
  • How to modify pipeline products for polarization calibration
  • Linear Polarization Calibration
  • Wide-field Polarization Imaging
  • Self-calibration
  • Analysis of Polarization Products

P-band continuum imaging data reduction tutorial: 3C129

  • This tutorial requires to download a dataset 26GB in size

This low frequency VLA tutorial for the observation of radio galaxy 3C 129 focuses on low frequency wide-fractional-bandwidth data in the sub GHz regime and demonstrates multi-frequency synthesis imaging with w-projection. This includes:

  • Basic flagging and evaluation
  • Automatic RFI Excision
  • Ionospheric Calibration
  • Self - Calibration
  • Widefield imaging

P-band spectroscopy tutorial: HI 21cm absorption in MG0414+0534 at z=2.64

  • This tutorial is based on an archival data-set of 142 Gb in size, but we will extract only a 15GB portion of this data-set to work on.

This VLA P-band tutorial is aimed at calibrating and making an image cube of line-emission centered on 390.6 MHz. It includes:

  • P-band spectral-line observing strategies
  • Basic flagging options
  • Low-frequency calibration and self-calibration
  • Spectral-line imaging

VLA Topical Guides

Flagging VLA Data in CASA

  • This tutorial requires to download a dataset 4.9GB in size

This tutorial describes different flagging techniques, including:

  • Identifying Problematic Antennas from the Operator Logs
  • Online Flags
  • Shadowing, zeroes, quacking, flagmanager, Hanning smoothing
  • Automatic RFI excision (TFCrop, RFlag)
  • Interactive Flagging (plotms, msview)
  • Flagging Summary & Report

Imaging VLA Data in CASA

  • This tutorial requires to download a dataset 1.2GB in size

The Imaging topical guide shows annotated examples of different imaging techniques that are applicable to different science applications. This tutorial includes:

  • An Introduction to the CLEAN algorithm, data and imaging weights, primary and synthesized beams
  • Clean Output Images
  • Dirty Image, Regular CLEAN & RMS Noise, CLEAN with different Weights
  • Multi-Scale CLEAN
  • Multi-Scale, Wide-Field CLEAN (w-projection)
  • Multi-Scale, Multi-Term Frequency Synthesis
  • Multi-Scale, Multi-Term Frequency, Widefield CLEAN
  • Imaging Outlier Fields
  • Primary Beam Correction
  • Imaging Spectral Cubes, Beam per Plane
  • Image Header, Image Conversion

VLA Multi-Configuration Data Combination

The VLA Data Combination Tutorial provides guidance on the combination of multi-configuration VLA data sets (in this case VLA A, B and C configurations). The data are re-weighted in two different ways, combined, and imaged. The guide also explains how to remove a time variable source from the data before combination.

Correcting for a Spectral Index in Bandpass Calibration

This tutorial explains how to obtain a bandpass solution when the bandpass calibrator is a source with an unknown spectral index. This is typically encountered at high frequency observations, where the standard VLA flux density calibrators are too weak for high signal-to-noise bandpass solutions.



VLA CASA Simulation Guide

The VLA Protoplanetary Disk Simulation Guide shows examples on how to simulate VLA data based on model images. The tutorial will explain the main simulation tools, apply different parameters to simulations, and compares the results to the VLA exposure calculator.

VLA CASA Pipeline Guide

The VLA CASA Pipeline Guide provides an example of a VLA CASA pipeline run. Whereas the VLA Pipeline Web Page describes the pipeline structure, requirements, execution options including restoration, pipeline output products, and pipeline modifications, this CASA guide is a detailed walkthrough of the weblog and provides interpretations of pipeline plots, tables, and Quality Assurance (QA) metrics.