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An Introduction to Simdata

An Introduction to Simdata. Scott Schnee (NRAO) Victoria Workshop – Jan 18, 2011. 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.

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An Introduction to Simdata

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  1. An Introduction to Simdata Scott Schnee (NRAO) Victoria Workshop – Jan 18, 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

  3. Model Image30Dor Spitzer IRAC 8um image from SAGE

  4. Model ImageResized and now at 230 GHz

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

  6. Scales Measured by ES Configuration Antenna Placement uv-coverage synthesized beam 2 hour observation

  7. Scales Measured by FS Compact Antenna Placement uv-coverage synthesized beam 2 hour observation

  8. Scales Measured by FS Extended Antenna Placement uv-coverage synthesized beam 2 hour observation

  9. Model Image in ES Configuration Model Image Convolved Model “Observed” Image 2 hour observation

  10. Model Image in FS Compact Model Image Convolved Model “Observed” Image 2 hour observation

  11. Model Image in FS Extended Model Image Convolved Model “Observed” Image 2 hour observation

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

  13. Basic Simdata Inputs

  14. FITS Image Basics • Coordinates • Brightness • Observing Frequency • Resolution (angular and spectral) • Polarization (if needed)

  15. modifymodel • modifymodel = True • skymodel = “30dor.fits” • inbright = ”0.1mJy/pixel” • indirection = "J2000 10:00:00 -40:00:00” • incell = "0.25arcsec” • incenter = "230GHz” • inwidth = '2GHz'

  16. setpointings • integration = '600s’ • mapsize = "” • pointingspacing = ""

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

  18. Simdata Output • analyze = True • showarray = True • showconvolved = True • showdifference = False • showfidelity = False

  19. Simdata Output

  20. Simdata Output

  21. Simdata Output - Viewer

  22. Other Simdata OptionsThermal Noise • thermalnoise = ‘tsys-atm’ • image = True • vis=‘$project.noisy.ms’

  23. Other Simdata OptionsThermal Noise Convolved Model No Thermal Noise Thermal Noise

  24. Other Simdata OptionsPhase Noise Convolved Model No Phase Noise Phase Noise

  25. Other Simdata OptionsPhase Noise • Create measurement set with simdata • Use the “toolkit” to add phase noise • http://casa.nrao.edu/docs/CasaRef/CasaRef.html • http://casaguides.nrao.edu/index.php?title=Corrupt • sm.openfromms("simPN.ms") • sm.settrop(mode='screen',pwv=1.0,deltapwv=0.15) • sm.corrupt() • sm.done() • Use clean (in CASA) to make the image

  26. Your Turn • Find a fits file of an object you want to image • Use simdata to see how it would look if observed with ALMA • Rescale image if necessary • Try different antenna configurations • Add noise if interested • Don’t be afraid to ask for help!

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