; UVMOD ;--------------------------------------------------------------- ;! Modify UV database by adding a model or models ;# TASK UV ANALYSIS MODELING ;----------------------------------------------------------------------- ;; Copyright (C) 1995, 1997, 2001 ;; Associated Universities, Inc. Washington DC, USA. ;; ;; This program is free software; you can redistribute it and/or ;; modify it under the terms of the GNU General Public License as ;; published by the Free Software Foundation; either version 2 of ;; the License, or (at your option) any later version. ;; ;; This program is distributed in the hope that it will be useful, ;; but WITHOUT ANY WARRANTY; without even the implied warranty of ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the ;; GNU General Public License for more details. ;; ;; You should have received a copy of the GNU General Public ;; License along with this program; if not, write to the Free ;; Software Foundation, Inc., 675 Massachusetts Ave, Cambridge, ;; MA 02139, USA. ;; ;; Correspondence concerning AIPS should be addressed as follows: ;; Internet email: aipsmail@nrao.edu. ;; Postal address: AIPS Project Office ;; National Radio Astronomy Observatory ;; 520 Edgemont Road ;; Charlottesville, VA 22903-2475 USA ;----------------------------------------------------------------------- UVMOD LLLLLLLLLLLLUUUUUUUUUUUU CCCCCCCCCCCCCCCCCCCCCCCCCCCCC 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 # 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 4.0 Number of sources CTYPE 0.0 5.0 Component type: 0 point, 1 Gaussian, others see help GMAX Peak value of sources GPOS (X,Y) position in asec GWIDTH (Major,Minor,PA) in asec,asec,deg ZEROSP Zero spacing flux for (1) I, (2) Q, (3) U and (4) V in Jy. FLUX Noise level in Jy/Weight. FACTOR Multiplication factor. QUAL If >0 then weights are reset to a value of 1. ---------------------------------------------------------------- UVMOD Type: Task Use: Modification of existing UV data by the addition of models. 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. 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. CTYPE......Type of each source: 1 Gaussian, 2 solid disk, 3 solid rectangle, 4 optically thin sphere, 5 exponential otherwise point. GMAX.......I polarization max of each source GPOS.......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 tangent plane and are applied with the W term taken into account (as of 1997-04-16). GWIDTH.....Model major and minor axis in arcsec and PA in degrees. Full width or full width to half maximum (GAUS). ZEROSP.....Zero spacing flux of (2) Q, (3) U and (4) V in Jy used with the first source only. 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. ---------------------------------------------------------------- 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 PURPOSE 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 disks. The five available models to choose from are 1) point source, 2) Gaussian, 3) solid disk 4) solid rectangle, and 5) optically thin sphere.. These models are first Fourier transformed and then added to the UV data. The resulting functions are: 1) Point -> A constant visibility amplitude is added to the data. The GWIDTH adverbs have no affect on this model. 2) 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)) 3) 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. 4) 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. 5) 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. 6) Exponential -> 'EXPD' 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. 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. ZEROSP: This adverb, array indices 2-4, allows you to add polarization to the first model component only. 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.