SIMDATA Simulation Shigehisa Takakuwa (ASIAA) ALMA Users Meeting 2011.

SIMDATA SimulationSIMDATA Simulation

Shigehisa Takakuwa (ASIAA)Shigehisa Takakuwa (ASIAA)

ALMA　 Users Meeting 2011

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

Theoretical model Images@ ALMA observing band

``Observed’’ Images

Theoretical Physical Parameters ofyour favorite astronomical objects

``Observed’’ Physical Parameters

2 SED fitting

ALMA Imaging Simulation

Radiative Transfer Code

Compare !!SciencePower of ALMA

ALMA observing Simulation

ALMA Observation

• Data we obtain are ``Visibilities V (u,v)’’,

V (u,v) = ∬ I (x,y) exp {-2πi (ux+vy)} dxdyx, y: Sky Spatial Coordinateu, v: Antenna Tracks projected on the sky

V (u,v) consists of amplitude and phase

Fourier-Transform of Source Images I (x,y)

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 NOTReal 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…

How to evaluate the imaging quantitatively ?

---> Introducing ``Fidelity’’

Fidelity (i, j) = --------------------------------------------abs[ Model (i, j) ]At each image pixel (i, j);

abs[Model (i, j) - Simulated (i, j)]

So Fidelity is an image.Pety et al. 2001

Model (J CMT SCUBA) 12-m Array only 12-m Array +TP 12-m Array +ACA

DecOff(arcsec)

RA Off (arcsec)

Fidelities

ε ERIDANI Debris Disk 8 5 0 μm @ distance of 1 3 pc

Greaves et al. 2 0 0 5

Model| Model - Simulation |

Fidelity =

Example of the ALMA Imaging Simulation:Debris Disk

ACA is crucial to recover the flux from debris disks.(Takakuwa et al. 2008)

ALMA Observing SimulatorTask ``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 imagewith the user-specified imaging parameters,such as weighting on the visibility sampling points.

Products from simdataSynthetic visibilities

A synthesized CLEANed image

Image of the Difference between the model and simulated image, and Fidelity

ALL you need is a model of the skyALMA. (E)VLA, SMA simulations possible

QuickTime˛ Ç∆ êLí£ÉvÉçÉOÉâÉÄ

ǙDZÇÃÉsÉNÉ`ÉÉÇ å©ÇÈÇΩÇflÇ…ÇÕïKóvÇ≈Ç∑ÅB

Simdata Example: Forming Planets in ProtoSimdata Example: Forming Planets in Protoplanetary Diskplanetary Disk

Proto-Planetary Disk Simulation

Effects of the Different antenna Effects of the Different antenna configurationsconfigurations

demodemodemodemo

Hands-on Exercise:Hands-on Exercise:Read input fits image into CASARead input fits image into CASA

PC with CASA installed

＋Input Image File(in FITS）

casapydefault(‘importfits’)fitsimage=‘input50pc_672GHz.fits’imagename=‘input50pc_672GHz’goviewer();

casapydefault(‘importfits’)fitsimage=‘input50pc_672GHz.fits’imagename=‘input50pc_672GHz’goviewer();

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=10000totaltime=‘1200s’graphics=‘both’image=Trueanalyze=Truego

Hands-on Exercise: simdata simulation, chHands-on Exercise: simdata simulation, changing input model parametersanging input model parameters

modifymodel=Trueincenter=‘230GHz’inwidth=‘2GHz’incell=‘0.0155arcsec’go