Karl G. Jansky VLA Tutorials

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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.

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

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

  • 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

Supernova Remnant 3C391: 6cm Polarimetry and Continuum Imaging, Mosaicking

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

Calibrate VLA full polarization data, image a mosaic of the region in full Stokes and create a spectral index map. Includes:

  • Inspecting data; basic flagging
  • Calibration
  • Image Analysis and Manipulation
  • Polarization Imaging
  • Spectral Index imaging
  • Self-calibration

3C129 P-band continuum imaging data reduction tutorial

  • 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
  • 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 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 and tables.

CASA Guide Versions

In addition to the most recent VLA casa guides, below we also provide links to older versions of the VLA CASA guides. Note that some graphs and links may be outdated, or, in some cases, actually point to the current CASA version as content was refreshed. For older CASA documentation, we refer to the links on Previous CASA Versions on the CASA home page.


CASA 5.0 / 5.1.2 versions


CASA 4.7 versions

CASA 4.6 versions

CASA 4.5 versions

CASA 4.4 versions

CASA 4.3 versions

CASA 4.2 versions

CASA 4.1 versions

CASA 3.4 versions

CASA 3.3 versions

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