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Exploring Simdata: A Tool for Predicting ALMA Observations

This presentation introduces Simdata, a versatile tool used for simulating astronomical observations with the ALMA telescope. It covers core functionalities, including how to input model images, adjust parameters such as antenna configuration and observing time, and predict how target images would appear when observed. The session outlines practical applications and workflows, offering resources like online guides and workshops for further learning. Join us to enhance your understanding of Simdata and its applications in radio astronomy.

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Exploring Simdata: A Tool for Predicting ALMA Observations

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  1. An Introduction to Simdata Scott Schnee (NRAO) AAS Splinter Meeting – Jan 12, 2011

  2. What is Simdata Good For? Take a model image and find out how it would look if observed with ALMA • Number of antennas • Antenna configuration • Length of observation • Noise* • Thermal Noise • Phase Noise

  3. Simdata is a versatile tool within CASATo learn more: • Go through online simdata guides • http://casaguides.nrao.edu/ • Go to one of our workshops or tutorials • http://science.nrao.edu/alma/training.php

  4. 30Dor from Spitzer IRAC 8μm from SAGE Resized and now at 230 GHz

  5. Fourier Transforms of Images From http://carmilumban-ap186.blogspot.com

  6. Scales Measured in Early Science Antenna Placement uv-coverage synthesized beam Point Spread Function bmaj = 1.0 bmin = 0.9 2 hour observation

  7. Full Science 12m Array - Compact Antenna Placement uv-coverage synthesized beam bmaj = 1.1 bmin = 0.96 2 hour observation Note lower sidelobes

  8. Model: Early Science Configuration Convolved Model Model Image “Observed” Image 2 hour observation

  9. Model: Full Science 12m Array - Compact Model Image Convolved Model “Observed” Image Large scale emission: Observe with ACA and possibly TPA 2 hour observation

  10. Basic Simdata Workflow • Start CASA • Input image file into Simdata • Predict what ALMA would see using Simdata • Compare ALMA image with input image

  11. Basic Simdata Inputs • Image / model of target • Observing time • Antenna configuration

  12. Basic Simdata Inputs Parameters that can be changed Current values of parameters Explanation of what the parameters are

  13. Basic Simdata Inputs

  14. Model Input FITS FileHeader must include: • Coordinates • Brightness units • Observing frequency • Pixel Scale (angular and spectral) • Polarization (if needed) • OR: Modify FITS image within Simdata

  15. predict • repodir = os.getenv("CASAPATH").split(' ')[0] • antennalist = repodir+"/data/alma/simmos/alma.early.250m.cfg"

  16. Simdata Output

  17. Simdata Output - Viewer http://casa.nrao.edu/CasaViewerDemo/casaViewerDemo.html

  18. Your Turn • Download CASA • http://casa.nrao.edu/ • Find/create an image of what you will observe • Use Simdata to see how it would look if observed with ALMA • Learn more • http://casaguides.nrao.edu • http://science.nrao.edu/alma/training.php

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