; CCMOD ;--------------------------------------------------------------- ;! generates clean components to fit specified source model ;# Task Imaging ;----------------------------------------------------------------------- ;; Copyright (C) 1995, 1998 ;; 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 ;----------------------------------------------------------------------- CCMOD LLLLLLLLLLLLUUUUUUUUUUUU CCCCCCCCCCCCCCCCCCCCCCCCCCCCC CCMOD: Task to generate clean components from a model source INNAME Image name (name) INCLASS Image name (class) INSEQ 0.0 9999.0 Image name (seq. #) INDISK 0.0 9.0 Disk drive # INVERS -1.0 46655.0 CC file ver. no.: 0 higest -1 new version OPCODE Model type: 'DISK','GAUS' FLUX Model flux BMAJ 0.0 Model major axis in pixels BMIN 0. Model minor axis in pixels BPA -360.0 360.0 Position angle of major axis PIXXY -100.0 8192.0 Model center in pixels BITER 0. Place results after comp # ---------------------------------------------------------------- CCMOD Type: Task Use: CCMOD generates a set of Clean components for a model source. These components are then inserted into the Clean components file (CC) associated with an image. This task is useful for generating clean components of an extended source of known parameters a priori. Further Cleaning (APCLN, IMAGR, etc) can then be done. Adverbs: INNAME......The image name (name). Standard defaults. INCLASS.....The image name (class). Standard defaults. INSEQ.......The image name (seq. #). 0 => highest. INDISK......The disk drive #. 0 => any. INVERS......The CC file ver #. 0 => highest current one. -1 => create new one. If none exists, one will be created in any case. Be careful with this. If you request some large number you will get it. OPCODE......The model type: 'DISK' or 'GAUS' or 'POIN' FLUX........The total flux density in the model BMAJ........The model major axis in asec. Diameter for 'DISK', FWHP for 'GAUS' in pixels BMIN........The model minor axis in pixels. BPA.........The position angle (deg) of the major axis. PIXXY.......(X,Y,...) position of center of the model in pixels. BITER.......Place model components after component BITER. Note that components BITER+1 through BITER+n get replaced by the model, where n is the number of cells with significant value. Set BITER = 0 or large to write at the end of the current CC file, retaining all current components. ---------------------------------------------------------------- CCMOD: Task to generate Clean components from a model source. DOCUMENTOR: Alan Bridle (NRAO-Charlottesville) RELATED PROGRAMS: APCLN, PHCLN, PRTCC PURPOSE As described in the documentation of APCLN, Clean algorithms attempt to answer the question "What is the distribution of amplitudes at the Clean component positions which best fits the visibility data, if we define the sky to be blank everywhere else ?" Clean can then be thought of a "search" for places where there should be components, and an adjustment of the intensities at these places to obtain the best agreement with the data. The user can greatly assist the search for appropriate locations for Clean components by telling Clean where the source is and what shape it should be. Specifying the "Clean Window" via NBOXES and BOX in APCLN gives the algorithm a boundary within which to hunt for emission, but still allows it to find components one at a time within this boundary by searching the residual map. This can (and does) lead to a scattering of Clean components through an extended region, with empty areas between them - a "pincushion" of components where an extended emission region may be more plausible. This is inefficient if the user KNOWS that the source being mapped should have emission EVERYWHERE within a certain boundary, i.e. that EVERY LOCATION within that boundary should have a Clean component whose amplitude is to be adjusted. CCMOD provides a means of telling APCLN that this is the case, by generating an initial list of Clean components from a specified model rather than by searching a map one location at a time. Two types of model are provided - DISKs and GAUSsians, selected by the OPCODE parameter. DISK is intended for use when mapping planets, the Sun, or other objects in which fine detail is superposed on a bright filled disk background. GAUS may find applications to sources where a bright diffuse region fades at the edges, e.g. lobes of extragalactic sources. FLUX is the total flux density in the model. BMAJ and BMIN are in units of pixels. Depending on edge effects, the total flux density actually put into the clean components may differ by 10% (or more for small objects) from the value in FLUX.