AIPS HELP file for SPMOD in 31DEC24
As of Thu Apr 25 2:03:36 2024
SPMOD: Task which inserts a spectral-line model into uv data
INPUTS
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 #
INLIST List of sources up to 9999
FLUX Noise level in Jy/Weight.
FACTOR Multiplication factor.
QUAL If >0 then weights are
reset to a value of 1.
DOHIST > 0 => list sources in
history file
BADDISK Disks to avoid for scratch
HELP SECTION
SPMOD
Type: Task
Use: Modification of existing UV data by the addition of spectral-line
models. UVMOD does continuum models including polarization and
spectral index, SPMOD adds objects as spectral-line features.
Adverbs:
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: in this case, no cross-polarization is
allowed so the output is really only 'HALF', 'I', or 'IV'.
TIMERANG...Time range of the data to be copied. In order: Start day,
hour, min. sec, end day, hour, min. sec. Days relative to
ref. date.
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
corrected.
(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
corrected.
IMAGR uses DOBAND as the nearest integer; 0.1 is therefore
"false".
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
SMOOTH(2).
DOACOR.....> 0 => include autocorrelations as well as cross
correlation data.
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.
INLIST.....Text file containing one line per source, giving
RR, DX, DY, Maj, Min, PA, type, line center, width, LL
blank separated free format and trailing zeros may be
omitted. The resulting NGAUS will be #lines in INLIST.
Limit 9999.
RR is the right-right flux, LL is the left-left flux
and an omitted LL is set equal to RR (but you can enter 0
for LL to have the line solely in RR or vice versa).
Note too that RR and or LL may be negative or positive.
DX, DY, Maj and Min are in arcseconds, PA in degrees,
line center and width (FWHM) are in channels
Channels are counted from BCHAN through ECHAN as 1 - N in
IF BIF, N+1 - 2N in IF BIF+1, etc.
Blank lines and lines beginning with # or ; (semi-colon)
are taken as comments
FLUX.......Noise level to be added (in Jy. per Weight).
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.
QUAL.......If QUAL > 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
> 0.
BADDISK....The disk numbers to avoid for scratch files (sorting
tables mostly).
EXPLAIN SECTION
SPMOD: Task which modifies UVDATA by scaling the existing data,
and adding a specified model (See also IMMOD).
RELATED PROGRAMS: UVMOD, MODIM, IMMOD
PURPOSE
SPMOD modifies an already existing UV data file by the addition of
one of several model types as spectral-line features. 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 disks.
The flux options allow you to model Zeman splitting by have two
components, one in RR and a different one in LL. You may also add
absorption features with RR and or LL negative.
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.
MAJ, MIN, PA :
The dimensions of the resulting functions are determined by MAJ, MIN
and PA (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
MAJ and MIN are both zero then all the models reduce to the point model.
FACTOR :
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.
Coordinate considerations:
FPOS is translated to an RA, Dec following the formula (assuming
no rotations):
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
geometry):
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.