AIPS HELP file for UVMOD in 31DEC21
As of Sun May 16 19:18:51 2021
UVMOD: Task which inserts a model into uv data
INNAME Input UV file name (name)
INCLASS Input UV file name (class)
INSEQ 0.0 9999.0 Input UV file name (seq. #)
INDISK 0.0 9.0 Input UV file disk unit #
SOURCES Source name
QUAL -10.0 Calibrator qualifier -1=>all
CALCODE Calibrator code ' '=>all
STOKES Stokes of output
TIMERANG Time range to use
SELBAND Bandwidth to select (kHz)
SELFREQ Frequency to select (MHz)
FREQID Freq. ID to select.
SUBARRAY 0.0 1000.0 Sub-array, 0=>all
BIF Low IF number to do
EIF Highest IF number to do
BCHAN 0.0 First channel included
ECHAN 0.0 last channel included
DOCALIB -1.0 101.0 > 0 calibrate data & weights
> 99 do NOT calibrate weights
GAINUSE CL (or SN) table to apply
DOPOL -1.0 10.0 If >0.5 correct polarization.
PDVER PD table to apply (DOPOL>0)
BLVER BL table to apply.
FLAGVER Flag table version
DOBAND -1.0 10.0 If >0.5 apply bandpass cal.
Method used depends on value
of DOBAND (see HELP file).
BPVER Bandpass table version
SMOOTH Smoothing function. See
HELP SMOOTH for details.
DOACOR Include autocorrelations?
OUTNAME Output UV file name (name)
OUTCLASS Output UV file name (class)
OUTSEQ -1.0 9999.0 Output UV file name (seq. #)
OUTDISK 0.0 9.0 Output UV file disk unit #
NGAUSS 0.0 9999.0 Number of sources
CTYPE 0.0 5.0 Component type: 0 point, 1
Gaussian, others see help
FMAX Peak value of sources
FPOS (X,Y) position in asec
FWIDTH (Major,Minor,PA) in
INLIST List of sources up to 9999
ZEROSP Zero spacing flux for (1) I,
(2) Q, (3) U and (4) V in Jy.
FLUX Noise level in Jy/Weight or
Jy if FACTOR=0.
DPARM Spectral indices to use
FACTOR Multiplication factor.
WTUV If >0 then weights are
reset to a value of 1.
DOHIST > 0 => list sources in
FQCENTER >= 0 -> center frequency axis
BADDISK Disks to avoid for scratch
Use: Modification of existing UV data by the addition of models.
INNAME.....Input image name (name). Standard defaults.
INCLASS....Input image name (class). Standard defaults.
INSEQ......Input image name (seq. #). 0 => highest.
INDISK.....Disk drive # of input image. 0 => any.
SOURCES....Source to be copied. ' '=> all; if any starts with a
'-' then all except ANY source named.
QUAL.......Qualifier of source to be copied. -1 => all.
CALCODE....Calibrator code of sources to copy. ' '=> all.
STOKES.....Specifies which STOKES parameters are written in the
output data set: ' ' => 'FULL'
'I','Q','U','V', 'IV', 'IQU', 'IQUV'
'RR','LL', 'RL', 'LR', 'RRLL', 'RLLR', 'RLRL'
'XX','YY', 'XY', 'YX', 'XXYY', 'XYYX', 'XYXY'
'HALF', 'CROS', and 'FULL' have sensible interpretations
depending on the Stokes present in the data. The last in
each of the 3 rows above == 'FULL'. Note that many
combinations of polarizations in the input and values
above are not supported.
TIMERANG...Time range of the data to be copied. In order: Start day,
hour, min. sec, end day, hour, min. sec. Days relative to
SELBAND....Bandwidth of data to be selected. If more than one IF is
present SELBAND is the width of the first IF required.
Units = kHz. For data which contain multiple
bandwidths/frequencies the task will insist that some form
of selection be made by frequency or bandwidth.
SELFREQ....Frequency of data to be selected. If more than one IF is
present SELFREQ is the frequency of the first IF required.
Units = MHz.
FREQID.....Frequency identifier to select (you may determine which is
applicable from the OPTYPE='SCAN' listing produced by
LISTR). If either SELBAND or SELFREQ are set, their values
override that of FREQID. However, setting SELBAND and
SELFREQ may result in an ambiguity. In that case, the task
will request that you use FREQID.
SUBARRAY...Sub-array number to copy. 0=>all.
BIF........First IF to include. 0 -> 1.
EIF........Last IF to include. 0 -> max.
BCHAN......First channel to copy. 0=>all.
ECHAN......Highest channel to copy. 0=>all higher than BCHAN
DOCALIB....If true (>0), calibrate the data using information in the
specified Cal (CL) table for multi-source or SN table for
single-source data. Also calibrate the weights unless
DOCALIB > 99 (use this for old non-physical weights).
GAINUSE....version number of the CL table to apply to multi-source
files or the SN table for single source files.
0 => highest.
DOPOL......If > 0 then correct data for instrumental polarization as
represented in the AN or PD table. This correction is
only useful if PCAL has been run or feed polarization
parameters have been otherwise obtained. See HELP DOPOL
for available correction modes: 1 is normal, 2 and 3 are
for VLBI. 1-3 use a PD table if available; 6, 7, 8 are
the same but use the AN (continuum solution) even if a PD
table is present.
PDVER......PD table to apply if PCAL was run with SPECTRAL true and
0 < DOPOL < 6. <= 0 => highest.
BLVER......Version number of the baseline based calibration (BL) table
to apply. <0 => apply no BL table, 0 => highest.
FLAGVER....specifies the version of the flagging table to be applied.
0 => highest numbered table.
<0 => no flagging to be applied.
DOBAND.....If true (>0) then correct the data for the shape of the
antenna bandpasses using the BP table specified by BPVER.
The correction has five modes:
(a) if DOBAND=1 all entries for an antenna in the table
are averaged together before correcting the data.
(b) if DOBAND=2 the entry nearest in time (including
solution weights) is used to correct the data.
(c) if DOBAND=3 the table entries are interpolated in
time (using solution weights) and the data are then
(d) if DOBAND=4 the entry nearest in time (ignoring
solution weights) is used to correct the data.
(e) if DOBAND=5 the table entries are interpolated in
time (ignoring solution weights) and the data are then
IMAGR uses DOBAND as the nearest integer; 0.1 is therefore
BPVER......Specifies the version of the BP table to be applied
0 => highest numbered table.
<0 => no bandpass correction to be applied.
SMOOTH.....Specifies the type of spectral smoothing to be applied to
a uv database . The default is not to apply any smoothing.
The elements of SMOOTH are as follows:
SMOOTH(1) = type of smoothing to apply: 0 => no smoothing
To smooth before applying bandpass calibration
1 => Hanning, 2 => Gaussian, 3 => Boxcar, 4 => Sinc
To smooth after applying bandpass calibration
5 => Hanning, 6 => Gaussian, 7 => Boxcar, 8 => Sinc
SMOOTH(2) = the "diameter" of the function, i.e. width
between first nulls of Hanning triangle and sinc
function, FWHM of Gaussian, width of Boxcar. Defaults
(if < 0.1) are 4, 2, 2 and 3 channels for SMOOTH(1) =
1 - 4 and 5 - 8, resp.
SMOOTH(3) = the diameter over which the convolving
function has value - in channels. Defaults: 1,3,1,4
times SMOOTH(2) used when input SMOOTH(3) < net
DOACOR.....> 0 => include autocorrelations as well as cross
OUTNAME....Output image name (name). Standard defaults.
OUTCLASS...Output image name (class). Standard defaults.
OUTSEQ.....Output image name (seq. #). 0 => highest unique
OUTDISK....Disk drive number of output image. 0 =>
highest number with sufficient space.
NGAUSS.....Number of sources 1 - 4 use CTYPE, FMAX, FPOS, and
FWIDTH; > 4, use INLIST file. Limit 9999.
Note, if INLIST not blank and NGAUSS > 1, the INLIST file
will be used BUT the value of NGAUSS will limit how many
components are read from INLIST. Set it large when you
use INLIST if you want the full contents of INLIST.
CTYPE......Type of each source: 1 Gaussian, 2 solid disk, 3 solid
rectangle, 4 optically thin sphere, 5 exponential
FMAX.......I polarization max of each source
FPOS.......Offset value of the X,Y centroid of the sources in
arcsec. Positive values mean increasing R.A. and DEC.
These are offsets in the coordinates with R.A. scaled by
cos(DEC) and are applied with the W term taken into
account (as of 1997-04-16). See Explain at the end.
FWIDTH.....Model major and minor axis in arcsec and PA in degrees.
Full width or full width to half maximum (GAUS).
INLIST.....Set this blank unless you want an input components list.
Text file containing one line per source, giving
I, DX, DY, Maj, Min, PA, type, spix, Dspix, Q, U, V
blank separated free format and trailing zeros may be
omitted. Used if NGAUSS > 1 and INLIST not blanks. The
resulting NGAUS will be min (NGAUSS, #lines in INLIST).
Limit 9999. Note that I, Q, U, V and the spectral
indexes are assumed to apply at the header (reference)
frequency. Any line in INLIST beginning with a $ or a #
is taken as a comment and ignored. Negative values for I
are allowed, but I=0 lines are ignored.
ZEROSP.....Zero spacing flux of (2) Q, (3) U and (4) V in Jy used
with the first source only and only if INLIST blank or
NGAUSS=1. For more polarization in models, use the
INLIST option. Be sure to put in the zeros (or other
values) for the parameters that precede the Q,U,V values
on each line in INLIST.
FLUX.......Noise level to be added (in Jy. per Weight or Jy if
FACTOR=0). This means, when FACTOR is not zero, that
the noise added is FLUX/sqrt(weight) so that FLUX scales
the data rms, assumed to be 1/sqrt(weight).
DPARM......(1-5) Spectral index to use for components 1,2,3,4,noise
(6-10) Spectral index curvature for comp 1,2,3,4,noise
A non-blank INLIST gives these if NGAUS > 1. DPARM(5)
and (10) still used for noise. See explain at the end.
Curvature numbers are based on base 10 logarithms with a
reference frequency of 1.0 GHz.
FACTOR.....Factor by which original data are multiplied before they
are added to the model. If FACTOR = 0 then only the model
will be left.
WTUV.......If WTUV > 0 then all Weights will be set to a
value of 1 in the output file.
DOHIST.....List sources in history file if NGAUS <= 4 and/or DOHIST
FQCENTER...> 0 => Change frequency axis reference pixel to
Nchan / 2 + 1
else => do not change reference pixel
BADDISK....The disk numbers to avoid for scratch files (sorting
UVMOD: Task which modifies UVDATA by scaling the existing data,
and adding a specified model (See also IMMOD).
DOCUMENTATION: Eric R. Nelson NRAO/VLA/UNM
DATE OF DOCUMENTATION: 14 JUNE 1983
RELATED PROGRAMS: IMMOD, UVMAP, APCLN, COMB
UVMOD modifies an already existing UV data file by the addition of
one of several model types. The original data may be scaled by a
multiplicative factor, including negative values and zero, before they
are added to the model. Random noise may also be added to the UV data.
The program could be useful in investigating the affects of CLEAN on a
specific geometry, or for removing models from data, i.e. planetary
The six available models to choose from are 0) point source, 1)
Gaussian, 2) solid disk 3) solid rectangle, 4) optically thin sphere,
and 5) exponential. These models are first Fourier transformed and
then added to the UV data. The resulting functions are:
0) Point -> A constant visibility amplitude is added to the
data. The GWIDTH adverbs have no affect on this
model. Used with CTYPE <= 0 or > 5.
1) Gaussian -> The function EXP(-3.559707*R**2) is added to
the UV data. The function R is given by:
R = Sqrt(UU**2 + VV**2) where
UU = BMAJ*(V*COS(BPA)+U*SIN(BPA))
VV = BMIN*(U*COS(BPA)-V*SIN(BPA))
2) Disk -> The function J1(R)/R is added to the UV data,
where J1 is the Bessel function of order 1 and R
is the same as above.
3) Rectangle -> The function SINC(UU)*SINC(VV) is added to
the UV data, where SINC(X) = SIN(X)/X. UU and
VV are defined as above for the Gaussian.
4) Sphere -> The function (SIN(A)/A - COS(A)) / (A*A) is
added to the UV data where
A = BMAJ * Sqrt (U*U + V*V)
A = max (A, 2 pi / 100)
The GWIDTH adverbs have no affect on this model.
5) Exponential -> The function
2 Pi / (1 + a * a * R * R) ** 3/2
is added to the UV data where R is defined in 2
above and a is Pi/ln(2).
Note that all functions are scaled by the total flux and a complex
vector representing the phase of the model before being added to the
scaled input visibility data. The spectral index is applied to make
the peak flux
log(F/F0) = spix * log(nu/nu0) + Dspix * log^2 (nu/nu0)
where F0 is the model peak flux at the header reference frequency
nu0. log functions are base 10.
BMAJ, BMIN, BPA :
In this discussion, BMAJ = GWIDTH(1,i) for the i'th component,
BMIN = GWIDTH(2,i) for the i'th component, and BPA = GWIDTH(3,i) for
the i'th component, The dimensions of the resulting functions are
determined by BMAJ, BMIN and BPA (position angle). For the Gaussian
the first two values are the FWHM of the two axis. For the Disk and
the Rectangle, the first two values are the absolute dimensions of the
two available axis. If BMAJ and BMIN are both zero then all the
models reduce to the point model.
This adverb, array indices 2-4, allows you to add polarization to
the first model component only.
The FACTOR term allows one to add a scaled version of the
original data to the model. FACTOR is simply multiplied by the
original data which is then added to the model. If FACTOR = 0, then
only the model will remain in the final UV data base.
FPOS is translated to an RA, Dec following the formula (assuming
Dec = Dec0 + FPOS(2)
RA = RA0 + FPOS(1) / cos (Dec0)
These are then turned into l,m,n for phase = ul + vm + wn as (for -SIN
l = cos (Dec) * sin (Ra-Ra0)
m = sin (Dec) * cos (Dec0) -
cos (Dec) * sin (Dec0) * cos (Ra-Ra0)
n = sin (Dec) * sin (Dec0) +
cos (Dec) * cos (Dec0) * cos (Ra-Ra0)
Suitable formulae are used for -NCP geometry as well.
Spectral index parameters are entered as:
x = log10 (freq / 1 GHz)
F = F0 * exp ((Spix + Dspix * x) * x)
where F is the flux and F0 is the flux at 1.0 GHz. The model fluxes
at the reference frequency are converted to fluxes at 1 GHz.