1 / 15

SIMDATA Simulation

ALMA Users Meeting 2011. SIMDATA Simulation. Shigehisa Takakuwa (ASIAA). Preparing for the ALMA Proposal. What can you really get with ALMA observations ?. Can ALMA provide you with what you want to see ?. --> ALMA Observing Simulations. ``Observed’’ Images.

toshi
Download Presentation

SIMDATA Simulation

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. ALMAUsers Meeting 2011 SIMDATA Simulation Shigehisa Takakuwa (ASIAA)

  2. Preparing for the ALMA Proposal What can you really get with ALMA observations ? Can ALMA provide you with what you want to see ? --> ALMA Observing Simulations

  3. ``Observed’’ Images ``Observed’’ Physical Parameters ALMA observing Simulation Theoretical model Images@ ALMA observing band Theoretical Physical Parameters of your favorite astronomical objects Radiative Transfer Code Compare !! ALMA Imaging Simulation • Science Power of ALMA 2 SED fitting

  4. ALMA Observation • Data we obtain are ``Visibilities V (u,v)’’, Fourier-Transform of Source Images I (x,y) V (u,v) = ∬ I (x,y) exp {-2πi (ux+vy)} dxdy x, y: Sky Spatial Coordinate u, v: Antenna Tracks projected on the sky V (u,v) consists of amplitude and phase

  5. ALMA Imaging --> To obtain I (x,y) Ideally: V (u,v) = ∬ I (x,y) exp {-2πi (ux+vy)} dxdy • In reality: Vobs (u,v) = S (u,v) ∬ I (x,y) • exp {-2πi (ux+vy)} dxdy • S(u,v): Sampling Function • Fourier-Transform of Vobs (u,v) is NOT Real I(x, y), but we call it Dirty-Image ID(x,y) Methods to guess real I(x,y) from ID (x,y) ---> Clean, MEM, etc…

  6. How to evaluate the imaging quantitatively ?---> Introducing ``Fidelity’’ At each image pixel (i, j); abs[ Model (i, j) ] Fidelity (i, j) = -------------------------------------------- abs[Model (i, j) - Simulated (i, j)] So Fidelity is an image. Pety et al. 2001

  7. Model | Model - Simulation | Example of the ALMA Imaging Simulation:Debris Disk Fidelity = ACA is crucial to recover the flux from debris disks. (Takakuwa et al. 2008)

  8. ALMA Observing Simulator Task ``simdata’’: One of the tasks in CASA, the ALMA data reduction software Create model visibilities from model images, with observing parameters such as the antenna location, specified by the user. Fourier-Transform the Visibility, and ``CLEAN’’ the image with the user-specified imaging parameters, such as weighting on the visibility sampling points.

  9. Products from simdata • Synthetic visibilities • A synthesized CLEANed image • Image of the Difference between the model and simulated image, and Fidelity ALMA. (E)VLA, SMA simulations possible ALL you need is a model of the sky

  10. Simdata Example: Forming Planets in Protoplanetary Disk

  11. Effects of the Different antenna configurations Proto-Planetary Disk Simulation

  12. demodemo

  13. Hands-on Exercise:Read input fits image into CASA Input Image File (in FITS） PC with CASA installed ＋ • casapy • default(‘importfits’) • fitsimage=‘input50pc_672GHz.fits’ • imagename=‘input50pc_672GHz’ • go • viewer();

  14. casapy • default(‘importfits’) • fitsimage=‘input50pc_672GHz.fits’ • imagename=‘input50pc_672GHz’ • go • viewer(); • default(‘simdata’) • skymodel = ‘input50pc_672GHz’ • project = ‘psim2’ (rm -rf psim2* for the 2nd time) • direction=‘center’ • mapsize=‘0.76arcsec’ • antennalist=‘/Applications/CASA.app/Contents/data/alma/simmos/alma.out20.cfg’ (Try different antenna configurations !) • imsize=[192,192] • threshold=‘1e-7Jy’ • niter=10000 • totaltime=‘1200s’ • graphics=‘both’ • image=True • analyze=True • go

  15. Hands-on Exercise: simdata simulation, changing input model parameters • modifymodel=True • incenter=‘230GHz’ • inwidth=‘2GHz’ • incell=‘0.0155arcsec’ • go

More Related