# setjy¶

setjy(vis='', field='', spw='', selectdata=False, timerange='', scan='', intent='', observation='', scalebychan=True, standard='Perley-Butler 2017', model='', modimage='', listmodels=False, fluxdensity=- 1, spix=0.0, reffreq='1GHz', polindex='', polangle='', rotmeas=0.0, fluxdict='', useephemdir=False, interpolation='nearest', usescratch=False, ismms=False)[source]

Fills the model column with the visibilities of a calibrator

[Description] [Examples] [Development] [Details]

Parameters
• vis (string=’’) - Name of input visibility file

• field (string=’’) - Select field using field id(s) or field name(s)

• spw (string=’’) - Select spectral window/channels

• selectdata (bool=False) - Other data selection parameters

selectdata = True
• timerange (string=’’) - Select data based on time range

• scan (string=’’) - Scan number range

• intent (string=’’) - Select observing intent

• observation (string=’’) - Select by observation ID(s)

• scalebychan (bool=True) - Scale the flux density on a per channel basis or else on a per spw basis

• standard (string=’Perley-Butler 2017’) - Flux density standard

standard = Perley-Butler 2017
• model (string=’’) - File location for field model

• listmodels (bool=False) - List the available models for VLA calibrators or Tb models for Solar System objects

• interpolation (string=’nearest’) - Method to be used to interpolate in time

standard = Perley-Butler 2013
• model (string=’’) - File location for field model

• listmodels (bool=False) - List the available models for VLA calibrators or Tb models for Solar System objects

• interpolation (string=’nearest’) - Method to be used to interpolate in time

standard = Perley-Butler 2010
• model (string=’’) - File location for field model

• listmodels (bool=False) - List the available models for VLA calibrators or Tb models for Solar System objects

standard = Butler-JPL-Horizons 2012
• listmodels (bool=False) - List the available models for VLA calibrators or Tb models for Solar System objects

• useephemdir (bool=False) - Use directions in the ephemeris table

standard = manual
• fluxdensity (int=-1) - Specified flux density in Jy [I,Q,U,V]; (-1 will lookup values)

• spix (double=0.0) - Spectral index (including higher terms) of I fluxdensity

• reffreq (string=’1GHz’) - Reference frequency for spix

• polindex (doubleVec=’’) - Coefficients of an expansion of frequency-dependent linear polarization fraction expression

• polangle (doubleVec=’’) - Coefficients of an expansion of frequency-dependent polarization angle expression (in radians)

• rotmeas (double=0.0) - Rotation measure (in rad/m^2)

standard = fluxscale
• fluxdict (record=’’) - Output dictionary from fluxscale

• usescratch (bool=False) - Will create if necessary and use the MODEL_DATA

Description

The setjy task sets the model visibility amplitude and phase associated with a flux density scale and a specified clean components image into the model column of the MS data set. The flux density (I,Q,U,V) for a point source calibrator can be entered explicitly. If no model is specified, then a point source at the phase center is assumed. For sources that are recognized flux calibrators (listed in Flux Calibrator Models ), setjy can calculate the flux densities as a function of frequency (and time, for some extragalactic sources classified as the variable sources and Solar System objects). Otherwise, the flux densities should be manually specified ( standard=’manual’).

Overview

The basic modes of operations are specified by the parameter, standard. As the name indicates, the bulk of its options are different flux density standards available in CASA as listed in Flux Calibrator Models. In addition, standard=’manual’ allows flux density scaling to be specified directly instead of using one for the flux density standards. And finally, standard=‘fluxscale’ allows the user to insert a flux density based on the python dictionary result from the fluxscale task, after the initial setjy on the primary flux calibrator, to insert proper flux density models for secondary calibrators in the MS.

By default the setjy task will cycle through all selected fields, spectral windows and channels, (one solution per spw with scalebychan = False) , setting the flux density either to 1 Jy (unpolarized), or if the source is recognized as one of the calibrators, to the flux density (assumed unpolarized) appropriate to the observing frequency.

Optionally, the MODEL_DATA column can be filled with the Fourier transform of the model image. But for any given MeasurementSet, the performance and data storage requirements are less demanding without the MODEL_DATA column. If usescratch=False, the model is stored as a ‘virtual’ model. The model parameters are saved either in the SOURCE_MODEL column in the SOURCE table (if one exists) or in the keyword of the main table in the MS and model visibilities are evaluated on the fly when processing calibration or plotting in plotms. The result containing flux densities for each spw is returned as a Python dictionary when it is executed as the function with arguments,

# For Example

setjy(vis=‘my.ms’…)


Manually setting Flux Densities: standard=‘manual’

With this mode, the flux densities and other relevant parameters necessary to describe the model can be entered manually. The following are the subparameters.

standard       =   'manual'        #  Flux density standard
fluxdensity    = [1, 0, 0, 0]      #  Specified flux density in Jy [I,Q,U,V]; (-1 will lookup values)
spix           =         []        #  Spectral index (including higher terms) of I fluxdensity
reffreq        =         ''        #  Reference frequency for spix
polindex       =         []        #  Coefficients of an expansion of frequency-dependent linear
#  polarization fraction expression
polangle       =         []        #  Coefficients of an expansion of frequency-dependent polarization
rotmeas        =        0.0        #  Rotation measure (in rad/m^2)


In the simplest version, the flux for Stokes I can be set via the fluxdensity subparameter as the first entry in a list. In the above example [1,0,0,0] setjy sets the flux to 1 Jy. Additional Stokes specifications can be set in remaining list members. All fluxdensity vales must be given in units of Jy. A spectral index can be provided via the spix and reffreq subparameters. Finally it is also possible to provide coefficients for the polarization fraction and angle as well as a rotation measure to define the model (polindex, polangle, rotmeas subparameters).

The spix subparamter can accept a list of values to include the spectral index of Stokes I in higher order terms, using the definition of the flux density at a frequency, $$\nu$$, $$S(\nu)=fluxdensity[0]*\frac{\nu}{reffreq}^{spix[0]+spix[1]*log(\nu/reffreq)+..}$$ . The reffreq is given by a string including the unit (e.g. ‘10GHz’, note that there is no space between the value and the unit). The polindex takes a list of coefficents ([p0, p1, p2…]) using the definition of frequency-dependent polarization index (PI) , where

$$PI = \frac{\sqrt{Q^2+U^2}}{I} = p0 + p1*\frac{\nu-reffreq}{reffreq} + p2*(\frac{\nu-reffreq}{reffreq})^2 + ...$$.

Similarly, the polangle subparameter takes a list of coefficients ([a0,a1,a2, ..]) using the definition of polarization angle ($$\chi$$), where

$$\chi = 0.5arctan\frac{U}{Q} = a0 + a1*\frac{\nu-reffreq}{reffreq} + a2*(\frac{freq-reffreq}{reffreq})^2 + ..$$.

Note

Some logics how these subparameters are used to determine flux densities:

• When Stokes Q and U flux densities are given in fluxdensity, the coefficient, p0 is determined from these flux densities and the entry for p0 in polindex is ignored. Also, a0 is determined from these flux density values and the entry for a0 in polangle is ignored.

• If Q and U flux densities in fluxdensity are set to 0.0, then polindex [0] and polangle [0] are used to determine Q and U at reffreq.

• When the frequency-dependent polindex and polangle are used, be sure to include all the coefficients for both polindex and polangle. Otherwise Q and U flux densities are not calculated correctly.

• If rotmeas is given, the Q and U that are determined from above parameters are further corrected for the Faraday rotation.

Using the Predefined Standards

For the VLA, the default source models are customarily point sources defined by the ’Baars’, ’Perley 90’, ’Perley-Taylor 99’, ’Perley-Butler 2010’, time-variable ’Perley-Butler 2013’, ‘Perley-Butler 2017’, ’Scaife-Heald 2012’, or ’Stevens-Reynolds 2016’ flux density scales (See Flux Calibrator Models for details; ’Perley-Butler 2017’ is the current standard by default), or point sources of unit flux density if the flux density is unknown. When ‘Perley-Bulter 2017’ is used and if any part of the frequencies of the relevant visibility data are outside the valid frequency range for each individual source as listed in Flux Calibrator Models, setjy issues warning log messages while it still proceeds to calcuate the flux densities and set the model visibility.

Most calibrator sources are based on radio emission from quasars and jets. The spectral indices of these sources are such that at (sub)mm wavelengths the majority of these sources become too weak and variable to reliably set the flux density scale. Alternatives are thermal objects such as planets, moons, and asteroids. Being Solar System objects, these objects do not move at the sidereal rate and may be (strongly) resolved. The standard=’Butler-JPL-Horizons 2010’ and the recommended standard=’Butler-JPL-Horizons 2012’ (for more information on the implemented models, see Flux Calibrator Models page and also ALMA Memo 594 1.) option of setjy includes flux density calibration using Solar System objects.

For ’Butler-JPL-Horizons 2012’ CASA currently supports the objects listed in Flux Calibrator Models to be applied to ALMA data. These names are recognized when they are used in the ’field’ parameter in setjy. In that case, setjy will obtain the geocentric distance and angular diameter at the time of the observation from a JPL–Horizons ephemeris and calculate model visibilities. Currently the objects are modeled as uniform temperature disks. Note that this model may oversimplify the real structure, in particular asteroids. The supported brightness temperature models for Solar System objects can be listed by selecting a standard and listmodels=True without setting any other parameters as shown below:

setjy(standard=‘Butler-JPL-Horizons 2012’, listmodels=True)


Each model contains temperatures at tabulated frequencies except for Mars. For Mars, the model temperatures are tabulated in time and frequency (see Flux Calibrator Models - Conventions, Data Formats for more details).

For selected asteroids, time variable models are available based on thermophysical modeling by T. Mueller (private communication) for January 1st, 2014 and beyond. Currently, the new models are available for Ceres, Pallas, and Vesta. A model is also available for Lutetia but using this source for ALMA absolute flux calibration is not advised. These new models are automatically chosen for the data taken after 2014 January 1, 0 hr UT. These models are also listed when the setjy task is executed with standard=‘Butler-JPL-Horizons 2012’ and listmodels=True. These model data files contain flux densities tabulated in time and frequency (see Flux Calibrator Models - Conventions, Data Formats for more details).

Flux density calculation with Solar System objects depends on ephemerides. The setjy task looks for the data in os.getenv(‘CASAPATH’).split()[0] + ‘/data/ephemerides/JPL-Horizons’. If no ephemeris for the right object at the right time is present, the calculation will fail. Ask the ALMA helpdesk to make an ephemeris. The very adventurous and well versed in python can try it using CASA’s recipes.ephemerides package:

import recipes.ephemerides as eph
help eph


CASA comes with ephemerides for several more objects, but they are intended for use with me.framecomet(), and are not (yet) suitable flux density calibrators. It is up to the observer to pick a good flux density calibrator (bright, spherical and featureless, on a circular orbit, in the right part of the sky, and not too resolved). Even some of the objects listed above may prove to require more sophisticated flux density models than are currently implemented in CASA. For many objects running casalog.filter(‘INFO1’) before running setjy will send more information to the logger.

Warning

The apparent brightness of objects in the Solar System will vary with time because of the Earth’s varying distance to these objects, if nothing else. If the field index of a flux calibrator spans several days, setjy should be run more than once, limiting each run to a suitable timerange by using the timerange, scan, and/or observation selection parameters. Note that it is the field index that matters, not the name. Typically concat assigns moving objects a new field index for each observation, so usually it is not necessary to select a time range in setjy. However, it is worth checking with listobs, especially for planets.

Using Calibration Models for Resolved Sources

For observations of Solar System objects using the ’Butler-JPL-Horizons 2010’ and ’Butler-JPL-Horizons 2012’ models, setjy will know and apply the flux distribution across the extended structure of the calibrators.

For other sources, namely VLA calibrator sources, a flux density calibrator can be resolved at the observing frequency and the point source model generated by setjy will not be appropriate. If available, a model image of the resolved source at the observing frequency may be used to generate the appropriate visibilities using the model subparameter (currently only available for standard=’Perley-Butler 2010’, standard=’Perley-Butler 2013’, and standard=’Perley-Butler 2017’). To do this, the model subparameter must include the full path to the model image. If the model subparameter is given only the file name, setjy will first search for the model image in the current working directory.

Also note that using setjy with a model image will only operate on that single source. Therefore, for different sources, setjy would need to be run multiple times (with different field settings). The default model images available are listed by listmodel=True and are found in the …/data/nrao/VLA/CalModels sub-directory of the CASA installation. Note the full path to the flux density calibrators may change depending on the installation directory or copies of these models can be placed in the current working directory.

Note

Currently available model images are:

3C138_P.im 3C138_L.im 3C138_S.im 3C138_C.im 3C138_X.im 3C138_U.im 3C138_K.im 3C138_A.im 3C138_Q.im

3C286_P.im 3C286_L.im 3C286_S.im 3C286_C.im 3C286_X.im 3C286_U.im 3C286_K.im 3C286_A.im 3C286_Q.im

3C48_P.im 3C48_L.im 3C48_S.im 3C48_C.im 3C48_X.im 3C48_U.im 3C48_K.im 3C48_A.im 3C48_Q.im

3C147_P.im 3C147_L.im 3C147_S.im 3C147_C.im 3C147_X.im 3C147_U.im 3C147_K.im 3C147_A.im 3C147_Q.im

3C123_P.im

3C196_P.im

3C295_P.im

3C380_P.im

These are all un-convolved images of AIPS CC lists. It is important that the model image not be one convolved with a finite beam; it must have units of Jy/pixel (not Jy/beam).

Note that setjy will rescale the flux in the models for known sources to match those it would have calculated. It will thus extrapolate the flux out of the frequency band of the model image to whatever spectral windows in the MS is specified (but will use the structure of the source in the model image).

If no source model is available, the uvrange selection may be needed during calibration to exclude the baselines where the resolution effect is significant. There is no hard and fast rule for this, though should be considered if the calibrator shows a drop of more than 10% on the longest baselines (use plotms to look at this). The antenna selection may also be needed if the calibrator is heavily resolved and there are few good baselines to the outer antennas. Note that uvrange may also be needed to exclude the short baselines on some calibrators that have extended flux not accounted for in the model.

Note: For the following models, hard-coded radius limits on the model images are applied automatically.

 3C286 3.0” 3C48 0.95” 3C147 0.85” 3C138 0.75”

Note: the calibrator guides for the specific telescopes usually indicate appropriate min and max for uvrange. For example, see the VLA Calibration Manual at: https://science.nrao.edu/facilities/vla/observing/callist for details on the use of standard calibrators for the VLA.

Bibliography

1

Butler 2012, ALMA Memo #594

Examples

Set flux density explictly

With standard=’manual’ (and selectdata=True), the parameters look like this. fluxdensity takes a list of flux densities, [I, Q, U, V] at reffreq. The same reffreq will be used as a reference frequecy for spix, polindex, and polange.

#  setjy :: Fills the model column with the visibilities of a
calibrator
vis                 =         ''        #  Name of input visibility file
field               =         ''        #  Field name(s)
spw                 =         ''        #  Spectral window identifier (list)
selectdata          =       True        #  Other data selection parameters
timerange      =         ''        #  Time range to operate on (for usescratch=T)
scan           =         ''        #  Scan number range (for usescratch=T)
intent         =         ''        #  Observation intent
observation    =         ''        #  Observation ID range (for usescratch=T)
scalebychan         =       True        #  scale the flux density on a per channel basis or else on
#   a per spw basis
standard            =   'manual'        #  Flux density
standard
fluxdensity    =         -1        #  Specified flux density [I,Q,U,V]; (-1 will lookup values)
spix           =        0.0        #  Spectral index (including higher terms) of I fluxdensity
reffreq        =     '1GHz'        #  Reference frequency for spix
polindex       =         []        #  Coefficients of an expansion of frequency-dependent
#   linear polarization fraction expression
polangle       =         []        #  Coefficients of an expansion of frequency-dependent
#   polarization angle expression
rotmeas        =        0.0        #  Rotation measure (in rad/m^2)
usescratch          =      False        #  Will create if necessary and use the MODEL_DATA


In the simplest form, setting a constant Stokes I flux density for a calibrator ( field=’0’) for all spw can be done as

setjy(vis='data.ms', field='0', fluxdensity=[3.5,0.0,0.0,0.0])


To set Stokes I flux density with spectral index and Stokes Q and U using frequency-dependent polarization index and polarization angle (in rad) also including rotation measure:

setjy(vis=‘data.ms’, standard='manual', field = ‘3C48’,
fluxdensity=[6.4861, 0, 0, 0], spix=[-0.630458,-0.132252],
reffreq="3000.0MHz”, polindex=[0.02143,0.0392,0.002349,-0.0230]
polangle=[-1.7233,1.569,-2.282,1.49], rotmeas=-68.0)


Use one of the predefined standards

Current default for standard is ‘Perley-Butler 2017’ and the parameters look like this (with selectdata=True):

#  setjy :: Fills the model column with the visibilities of a calibrator
vis                 =         ''        #  Name of input visibility file
field               =         ''        #  Field name(s)
spw                 =         ''        #  Spectral window identifier (list)
selectdata          =       True        #  Other data selection parameters
timerange      =         ''        #  Time range to operate on (for usescratch=T)
scan           =         ''        #  Scan number range (for usescratch=T)
intent         =         ''        #  Observation intent
observation    =         ''        #  Observation ID range (for usescratch=T)
scalebychan         =       True        #  scale the flux density on a per channel basis or else on a per spw basis
standard            = 'Perley-Butler 2017' #  Flux density standard
model          =         ''        #  File location for field model
listmodels     =      False        #  List the available modimages for VLA calibrators or Tb models for Solar System objects
interpolation  =  'nearest'        #  method to be used to interpolate in time
usescratch          =      False        #  Will create if necessary and use the MODEL_DATA


In the most simplest case, using the default stanadard, if field=’0’ is one of the known sources as listed in Flux Calibrator Models (e.g. 3C286), the following will set appropriate channel dependent flux densities for all spws.

setjy(vis='data.ms', field='0')


For selected spws with field specified by the source name:

setjy(vis='data.ms', field='3C286', spw='0,2')


With a model image:

setjy(vis='ngc7538_XBAND.ms', field='0', modimage='3C48_X.im')


Note that if there is no 3C48_X.im in the current directory, setjy looks for it in the default model data image directory.

An example for a Solar System object as a flux calibrator using using data from the M99 tutorial in CASA Guides:

setjy(vis=’c0104I’, field=’MARS’, spw=’0~2’, standard=’Butler-JPL-Horizons 2012’)


To list supported models for the relevant standard, set istmodels=True and select standard (no need to set vis):

setjy(listmodels=True)


This will show a list of the VLA model images along with their full paths to the terminal:

No candidate modimages matching '*.im\* \*.mod*' found in .
Candidate modimages (*) in
/users/ttsutsum/casabuilds/data/nrao/VLA/CalModels:
3C138_A.im 3C138_L.im 3C138_U.im 3C147_C.im 3C147_Q.im
3C147_X.im 3C286_K.im 3C286_S.im 3C48_A.im  3C48_L.im
3C48_U.im
3C138_C.im 3C138_Q.im 3C138_X.im 3C147_K.im 3C147_S.im
3C286_A.im 3C286_L.im 3C286_U.im 3C48_C.im  3C48_Q.im
3C48_X.im
3C138_K.im 3C138_S.im 3C147_A.im 3C147_L.im 3C147_U.im
3C286_C.im 3C286_Q.im 3C286_X.im 3C48_K.im  3C48_S.im  README


Similarly, for Solar System objects (e.g. standard=’Butler-JPL-Horizons 2012’), Tb models and new time asteroid models are listed by:

setjy(standard='Butler-JPL-Horizons 2012', listmodels=True)


This will show a list looks like below in the terminal:

Tb models of solar system objects available for
Butler-JPL-Horizons 2012 (*Tb*.dat) in
/users/ttsutsum/casabuilds/data/alma/SolarSystemModels:
Callisto_Tb.dat  Europa_Tb.dat    Io_Tb.dat
Jupiter_Tb.dat   Mars_Tb_time.dat Pallas_Tb.dat
Uranus_Tb.dat    Vesta_Tb.dat
Ceres_Tb.dat     Ganymede_Tb.dat  Juno_Tb.dat
Mars_Tb.dat      Neptune_Tb.dat   Titan_Tb.dat
Venus_Tb.dat
Time variable models of asteroids available for
Butler-JPL-Horizons 2012 [only applicable for the observation
date 2014.01.01 0UT and beyond] (*fd_time.dat) in
/users/ttsutsum/casabuilds/data/alma/SolarSystemModels:
Ceres_fd_time.dat   Lutetia_fd_time.dat Pallas_fd_time.dat
Vesta_fd_time.dat

Development

Parameter Details

Detailed descriptions of each function parameter

vis (string='') - Name of input visibility file
Default: none
Example: vis=’ngc5921.ms’
field (string='') - Select field using field id(s) or field name(s)
Default: ‘’ (all fields, but run setjy one field
at a time)

Use ‘go listobs’ to obtain the list id’s or
names. If field string is a non-negative integer,
it is assumed a field index, otherwise, it is
assumed a field name.
Examples:
field=’0~2’; field ids 0,1,2
field=’0,4,5~7’; field ids 0,4,5,6,7
field=’3C286,3C295’; field named 3C286 and
3C295
field = ‘3,4C*’; field id 3, all names
starting with 4C
spw (string='') - Select spectral window/channels
Default: ‘’ (all spectral windows)
NOTE: setjy only selects by spectral window, and
ignores channel selections. Fine-grained control
could be achieved using (and possibly
constructing) a cube for modimage.
selectdata (bool=False) - Other parameters for selecting part(s) of the MS to
operate on.
Default: False
Options: False|True
Currently all time-oriented and most likely only
of interest when using a Solar System object as a
calibrator.
timerange (string='') - Select data based on time range
Subparameter of selectdata=True
Default = ‘’ (all)
Examples:
timerange =
‘YYYY/MM/DD/hh:mm:ss~YYYY/MM/DD/hh:mm:ss’
(Note: if YYYY/MM/DD is missing date defaults
to first day in data set.)
timerange=’09:14:0~09:54:0’ picks 40 min on
first day
timerange= ‘25:00:00~27:30:00’ picks 1 hr to 3
hr 30min on NEXT day
timerange=’09:44:00’ pick data within one
integration of time
timerange=’>10:24:00’ data after this time
scan (string='') - Scan number range
Subparameter of selectdata=True
Default: ‘’ = all
Example:scan=’1~5’
For multiple MS input, a list of scan strings can
be used:
scan=[‘0~100’,’10~200’]
scan=’0~100; scan ids 0-100 for all input MSes
Check ‘go listobs’ to insure the scan numbers are
in order.
intent (string='') - Select observing intent
Default: ‘’ (all
Example: using wildcard characters,
intent=”CALIBRATE_AMPLI” will match field(s)
contains CALIBRATE_AMPLI in a list of intents
WARNING: If a source with a specific field id has
scans that can be distinguishable with intent
selection, one should set
usescatch=True. Otherwise, any existing model of
the source may be cleared and overwritten even if
the part of the scans not selected by intent.
observation (string='') - Select by observation ID(s)
Subparameter of selectdata=True
Default: ‘’ = all
Example: observation=’0~2,4’
scalebychan (bool=True) - Scale the flux density on a per channel basis?
Default: True
Options: True|False
This determines whether the fluxdensity set in
the model is calculated on a per channel
basis. If False then it only one fluxdensity
value is calculated per spw. (Either way, all
channels in spw are modified.) It is effectively
True if fluxdensity[0] > 0.0.
standard (string='Perley-Butler 2017') - Flux density standard, used if fluxdensity[0] less than 0.0
Default: ‘Perley-Butler 2017’
Options: ‘Baars’, ‘Perley 90’, ‘Perley-Taylor
95’, ‘Perley-Taylor 99’, ‘Perley-Butler 2010’,
‘Perley-Butler 2013’, ‘Perley-Butler 2017’,
‘Scaife-Heald 2012’, ‘Stevens-Reynolds 2016’,
‘Butler-JPL-Horizons 2010’, ‘Butler-JPL-Horizons
2012’, ‘manual’ ‘fluxscale’
All but the last four options are for
extragalactic calibrators. The two ‘Butler-JPL’
standards are for Solar System objects. Note that
Scaife-Heald 2012 is for the low frequencies
(mostly valid for the frequency range,
30-300MHz).
Flux density calculation with Solar System
objects depends on ephemerides. The setjy task
looks for the data in
os.getenv(‘CASAPATH’).split()[0] +
‘/data/ephemerides/JPL-Horizons’. If no ephemeris
for the right object at the right time is
present, the calculation will fail. Ask the
helpdesk to make an ephemeris.
model (string='') - Model image (I only) for setting the model visibilities.
Subparameter of standard=”Perley-Butler 2010”,
“Perley-Butler 2013”, and “Perley-Butler 2017”
Default: ‘’ (do not use a model image)
The model can be a cube, and its channels do not
have to exactly match those of vis. It is
recommended to use model for sources that are
resolved by the observation, but the
Butler-JPL-Horizons standard supplies a basic
model of what several Solar System objects look
like. Each field must be done separately when
using a model image.
Both the amplitude and phase are calculated. At
the AOC or CV, the models are located in
casa[‘dirs’][‘data’] + ‘/nrao/VLA/CalModels/’,
e.g. /usr/lib/casapy/data/nrao/VLA/CalModels/3C286_L.im
lib64
for a match in ‘.’, ‘./CalModels’, and any
CalModels directories within the
casa[‘dirs’][‘data’] tree (excluding certain
branches).
Note that model should be deconvolved, i.e. a set
of clean components instead of an image that has
been convolved with a clean beam.
modimage (string='') - File location for field model
Deprecated
listmodels (bool=False) - List the available models for VLA calibrators or Tb
models for Solar System objects
Subparameter of standard=”Perley-Butler 2010”,
“Perley-Butler 2013”, and “Perley-Butler 2017”
Default: False
Options: False|True
If True, do nothing but list candidates for model
(for extragalactic calibrators) that are present
on the system. It looks for .im .mod in
. including its sub-directories but skipping any
CalModels directories in the casa[‘dirs’][‘data’]
tree. It does not check whether they are
appropriate for the MS! If
standard=’Butler-JPL-Horizons 2012’, Tb models
(frequency-dependend brightness temperature
models) for Solar System objects used in the
standard. For standard=’Butler-JPL-Horizons
2010’, the recognized Solar System objects are
listed.
fluxdensity (int=-1) - Specified flux density in Jy [I,Q,U,V]
Subparameter of standard=”manual”
Default: -1 (uses [1,0,0,0] flux density for
unrecognized sources, and standard flux densities
for ones recognized by the default standard
Perley-Butler 2010).
Only one flux density can be specified at a
time. The phases are set to zero.
setjy will try to use the standard if fluxdensity
is not positive.
Examples:
fluxdensity=-1 will use the default standard
for recognized calibrators (like 3C286, 3C147
and 3C48) and insert 1.0 for selected fields
with unrecognized sources.
field = ‘1’; fluxdensity=[3.2,0,0,0] will put
in a flux density of I=3.2 for field=’1’
At present (June 2000), this is the only method
to insert apolarized flux density model.
Example: fluxdensity=[2.63,0.21,-0.33,0.02]
will put in I,Q,U,V flux densities of
2.63,0.21,-0.33, and 0.02, respectively, in
the model column.
spix (double=0.0) - Spectral index for I flux density
Subparameter of standard=”manual”
Default: [] =>0.0 (no effect)
Options: a float or a list of float values
S = fluxdensity *
(freq/reffreq)**(spix[0]+spix[1]*log(freq/reffreq)+..)
Only used if fluxdensity is being used.
IMPORTANT: If fluxdensity is positive, and spix
is nonzero, then reffreq must be set too!
It is applied in the same way to all
polarizations, and does not account for Faraday
rotation or depolarization.
Example: [-0.7, -0.15] for alpha and a curvature term
reffreq (string='1GHz') - Reference frequency for spix
Subparameter of standard=”manual”
Default: ‘1GHz’ (this is only here to prevent
division by 0!)
Given with a unit with an optional frequency
frame (if the frame is not given, LSRK is
assumed). There should be no space between the
value and the unit (e.g. ‘100.0GHz’ or ‘TOPO
100.0GHz’ are correct but with ‘100.0 GHz’ you
will see a warning message that it will be
defaulted to LSRK).
Example: ‘86.0GHz’, ‘TOPO 86.0GHz’, ‘4.65e9Hz’
NOTE: If the flux density is being scaled by
spectral index, then reffreq must be set to
whatever reference frequency is correct for the
given fluxdensity and spix. It cannot be
determined from vis. On the other hand, if spix
is 0, then any positive frequency can be used
(and ignored).
polindex (doubleVec='') - Coefficients of the frequency-dependent linear
polarization index (polarization fraction)
Subparameter of standard=”manual”
Default: []
Expressed as pol. index = sqrt(Q^2+U^2)/I = c0 +
c1*((freq-reffreq)/reffreq) +
c2*((freq-reffreq)/reffreq)^2 + .. When Q and U
flux densities are given fluxdensity, c0 is
determined from these flux densities and the
entry for c0 in polindex is ignored. Or Q and U
flux densities in fluxdensity can be set to 0.0
and then polindex[0] and polangle[0] are used to
determine Q and U at reffreq.
Example: [0.2, -0.01] (= [c0,c1])
polangle (doubleVec='') - Coefficients of the frequency-dependent linear
Subparameter of standard=”manual”
Default: []
Expressed as pol. angle = 0.5*arctan(U/Q) = d0 +
d1*((freq-reffreq)/reffreq) +
d2*((freq-reffreq)/reffreq)^2 + .. When Q and U
flux densities are given in fluxdensity, d0 is
determined from these flux densities and the
entry for d0 in polangle is ignored. Or Q and U
flux densities in fluxdensity can be set to 0.0
and then polindex[0] and polangle[0] are used to
determine Q and U at reffreq. Here polangle
parameters are assumed to represent the intrinsic
polarization angle.
Example: [0.57, 0.2] (=[d0,d1])
rotmeas (double=0.0) - Rotation measure (in rad/m^2)
Subparameter of standard=”manual”
Default: 0.0
Note on the use of polindex, polangle and rotmeas
When the frequnecy-dependent polindex and
polangle are used, be sure to include all the
coefficients of both polindex and polangle to
describe frequency depencency. Otherwise
frequency-dependent Q and U flux densities are
not calculated correctly. If rotmeas is given,
the calculated Q and U flux densities are then
fluxdict (record='') - Output dictionary from fluxscale
Subparameter of standard=”fluxscale”
Using the flexibly results, the flux density,
spectral index, and reference frequency are
extracted and set to fluxdensity, spix, and
reffreq parameters, respectively. The field and
spw selections can be used to specify subset of
the fluxdict to be used to set the model. If they
are left as default (field=””, spw=””) all fields
and/or spws in the fluxdict (but those spws with
fluxd=-1 will be skipped) are used.
useephemdir (bool=False) - Use directions in the ephemeris table for the solar
system object?
Subparameter of standard=”Butler-JPL-Horizons
2012”,
Default: False
Options: False|True
interpolation (string='nearest') - Method to be used to interpolate in time for the time
variable sources (3C48,3C138,3C147).
Subparameter of standard=”Perley-Butler 2013”,
and “Perley-Butler 2017”
Default: ‘nearest’
Options: ‘nearest|linear|cubic|spline’
This parameter is ignored for other non-variable
sources in the standard.
usescratch (bool=False) - Will create if necessary and use the MODEL_DATA
Default: False
Options: False|True
* If False: ‘virtual’ model is created. The model
information is saved either in the SOURCE_MODEL
column in the SOURCE table (if one exists) or
in the keyword of the main table in the MS and
model visibilities are evaluated on the fly
when calculating calibration or plotting in
plotms.
* If True: the model visibility will be evaluated
and saved on disk in the MODEL_DATA column.
This will increase your ms in size by a factor
of 1.5 (w.r.t. the case where you only have
the DATA and the CORRECTED_DATA column). Use
True if you need to interact with the
MODEL_DATA in python, say. Also, use True if
you need finer than field and spw selections
using scans/time (and when use with intent
selection, please see WARNING section in the
intent parameter description).
By running usescratch=T, it will remove the
existing virtual model from previous
runs. usescratch=F will not remove the existing
MODEL_DATA but in subsequent process the virtual
model with matching field and spw combination
will be used if it exists regardless of the
presence of the MODEL_DATA column.
NOTE: for usescratch=False, timerange, scan, and
observation are ignored (i.e. time-specific
virtual model is not possible.).
VERY IMPORTANT: The current implementation of
time-dependent models (e.g. ephemerides sources)
within setjy is incompatible with the use of the
virtual model column. Please use ephemerides source
models only with usescratch=True
ismms (bool=False)` - to be used internally for MMS