simalma – Simulation task for ALMA – simulation task

Description

This task simulates ALMA observation including 12-m, ACA 7-m and total power arrays, and images and analyzes simulated data.

This task makes multiple calls to simobserve (to calculate visibilities and total power spectra), followed by gridding of total power spectra (if total power is requested), concatenation of the simulated visibilities, calls to the simanalyze task for visibility inversion and deconvolution and calculation of difference and fidelity images, and feathering of single dish and interferometric data.

These steps may not all be familiar to new users, so the simalma task runs by default in a “dryrun” mode, in which it assesses the user’s input parameters and sky model, and prints an informational report including the required calls to other CASA tasks, both to the screen and to a text file in the project directory (defined below).

The user can modify their parameters based on the information, then either run with dryrun=False to actually call the other tasks to create the simulated data, or run the other tasks individually one at a time to better understand and control the process.

NOTE The ALMA project is refining the optimal method of combining the three types of data. If that best practice is changed after this release of CASA, the user can control the process by modifying the calls to the other CASA tasks.

Parameters

Title

Parameter	Default	Description
project	'sim'	root prefix for output file names
dryrun	True	dryrun=True will only produce the informative report, not run simobserve/analyze
skymodel	''	model image to observe
inbright	''	scale surface brightness of brightest pixel e.g. “1.2Jy/pixel”
indirection	''	set new direction e.g. “J2000 19h00m00 -40d00m00”
incell	''	set new cell/pixel size e.g. “0.1arcsec”
incenter	''	set new frequency of center channel e.g. “89GHz” (required even for 2D model)
inwidth	''	set new channel width e.g. “10MHz” (required even for 2D model)
complist	''	componentlist to observe
compwidth	'"8GHz"'	bandwidth of components
setpointings	True
ptgfile	'$project.ptg.txt'	list of pointing positions
integration	'10s'	integration (sampling) time
direction	numpy.array( [  ] )	“J2000 19h00m00 -40d00m00” or “” to center on model
mapsize	numpy.array( [ '','' ] )	angular size of map or “” to cover model
antennalist	numpy.array( [ 'alma.cycle1.1.cfg','aca.cycle1.cfg' ] )	antenna position files of ALMA 12m and 7m arrays
hourangle	'transit'	hour angle of observation center e.g. -3:00:00, or “transit”
totaltime	numpy.array( [ '20min','1h' ] )	total time of observation; vector corresponding to antennalist
tpnant	int(0)	Number of total power antennas to use (0-4)
tptime	'0s'	total observation time for total power
pwv	float(0.5)	Precipitable Water Vapor in mm. 0 for noise-free simulation
image	True	image simulated data
imsize	numpy.array( [ int(128),int(128) ] )	output image size in pixels (x,y) or 0 to match model
imdirection	''	set output image direction, (otherwise center on the model)
cell	''	cell size with units or “” to equal model
niter	int(0)	maximum number of iterations (0 for dirty image)
threshold	'0.1mJy'	flux level (+units) to stop cleaning
graphics	'both'	display graphics at each stage to [screen|file|both|none]
verbose	False
overwrite	False	overwrite files starting with $project

Parameter Explanations

project

'sim'

root prefix for output file names

dryrun

True

dryrun=True will only produce the informative report, not run simobserve/analyze

skymodel

''

model image to observe

inbright

''

scale surface brightness of brightest pixel e.g. “1.2Jy/pixel”

indirection

''

set new direction e.g. “J2000 19h00m00 -40d00m00”

incell

''

set new cell/pixel size e.g. “0.1arcsec”

incenter

''

set new frequency of center channel e.g. “89GHz” (required even for 2D model)

inwidth

''

set new channel width e.g. “10MHz” (required even for 2D model)

complist

''

componentlist to observe

compwidth

'"8GHz"'

bandwidth of components

setpointings

True

ptgfile

'$project.ptg.txt'

list of pointing positions

integration

'10s'

integration (sampling) time

direction

numpy.array( [  ] )

“J2000 19h00m00 -40d00m00” or “” to center on model

mapsize

numpy.array( [ '','' ] )

angular size of map or “” to cover model

antennalist

numpy.array( [ 'alma.cycle1.1.cfg','aca.cycle1.cfg' ] )

antenna position files of ALMA 12m and 7m arrays

hourangle

'transit'

hour angle of observation center e.g. -3:00:00, or “transit”

totaltime

numpy.array( [ '20min','1h' ] )

total time of observation; vector corresponding to antennalist

tpnant

int(0)

Number of total power antennas to use (0-4)

tptime

'0s'

total observation time for total power

pwv

float(0.5)

Precipitable Water Vapor in mm. 0 for noise-free simulation

image

True

image simulated data

imsize

numpy.array( [ int(128),int(128) ] )

output image size in pixels (x,y) or 0 to match model

imdirection

''

set output image direction, (otherwise center on the model)

cell

''

cell size with units or “” to equal model

niter

int(0)

maximum number of iterations (0 for dirty image)

threshold

'0.1mJy'

flux level (+units) to stop cleaning

graphics

'both'

display graphics at each stage to [screen|file|both|none]

verbose

False

overwrite

False

overwrite files starting with $project