; SETJY ;--------------------------------------------------------------- ;! Task to enter source info into source (SU) table. ;# TASK CALIBRATION ;----------------------------------------------------------------------- ;; Copyright (C) 1995-1996, 2000 ;; 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 ;----------------------------------------------------------------------- ;--------------------------------------------------------------- SETJY LLLLLLLLLLLLUUUUUUUUUUUU CCCCCCCCCCCCCCCCCCCCCCCCCCCCC SETJY Task to enter source info into source (SU) table. INNAME Input image name (name) INCLASS Input image name (class) INSEQ 0.0 9999.0 Input image name (seq. #) INDISK 0.0 9.0 Input image disk unit # SOURCES Sources to modify. QUAL -10.0 Source qualifier -1=>all BIF 0.0 Low IF # for flux density EIF 0.0 High IF # for flux density ZEROSP I,Q,U,V flux density (Jy) OPTYPE ' ' => use other adverbs for required operation 'CALC' => determine 3C286/3C48/1934 fluxes from standard formulae 'REJY' => reset source fluxes to zero. 'REVL' => reset velocity to zero 'RESE' => reset fluxes & velocities to zero. CALCODE New calibrator code: '----' => change to blank SYSVEL Velocity of source (km/s) RESTFREQ Line rest frequency (Hz) VELTYP Velocity type 'LSR,'HELIO' VELDEF Velocity definition 'RADIO', 'OPTICAL' FREQID FQ table entry to use for velocity information and 'CALC' option APARM (1): Pixel to which SYSVEL refers ( 0=>1) (2): Only for 'CALC' option: <= 0 => use latest VLA values (1999.2) or, for 1934-638, the ATCA value of 30Jul94. 1 => use Baars values or old ATCA/PKS values for 1934-638 2 => use VLA 1995.2 values or, for 1934-638, the ATCA value of 30Jul94. >= 3 => use oldest VLA values (1990) or, for 1934-638, the ATCA value of 30Jul94. ---------------------------------------------------------------- SETJY Task: SETJY enters source information into the source (SU) table. 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....The list of sources. '*' = all; a "-" before a source name means all except ANY source named. All ' ' =>all. QUAL.......Only sources with a source qualifier number in the SU table matching QUAL will be modified if QUAL is not -1. BIF........The lowest IF number for which the given flux densities are valid. 0 => 1. EIF........The highest IF number for which the given flux densities are valid. 0 => all. ZEROSP.....The I, Q, U, and V flux densities in JY. If ZEROSP(5) < 0.0 then the flux densities are not changed (i.e. only calibrator codes are changed). all 0 => no change. OPTYPE.....' ' => use ZEROSP values for the source flux densities and SYSVEL for source velocity. 'CALC' => use the standard Baars et al formulae and frequency information in the header to determine the flux densities of the primary calibrators 3C286, 3C48 and 3C147 (IAU style names in B1950 or J2000 are also recognized by SETJY). Any selected sources with a recognized name will have fluxes calculated. Australia Telescope source 1934-638 is also recognized (J2000 only but can start with P). (see APARM(2) for polynomial selection). 'REJY' => reset source flux densities to zero for source(s) specified. 'REVL' => reset velocity to zero for source(s) specified. 'RESE' => do both 'REJY' and 'REVL' operations. CALCODE....The 4 character calibrator code to be inserted. ' ' => no change, '----' => change to blank, '*' is not allowed. NOTE that CALCODE is not part of the source selection in SETJY as it is in other tasks. SYSVEL.....The velocity of the source (in km/s) per IF. 0 => no change. If 0 is desired use 1.0E-10. RESTFREQ...Rest frequency of line (Hz) per IF; the value used is the sum of RESTFREQ(1)+RESTFREQ(2). 0=>no change VELTYP.....Velocity system ('LSR','HELIO'); ' '=> no change. VELDEF.....Definition of velocity, 'RADIO' or 'OPTICAL'; ' ' = > no change. FREQID.....Frequency identifier to select (you may determine which is applicable from the OPTYPE='SCAN' listing produced by LISTR). This is needed to set the frequency for flux computations in CALC OPTYPE. It is also needed to estimate the width of a line channel in km/s for calculation of velocity info. SET IT on CALC. APARM......(1) The frequency pixel (or channel) to which the velocity refers. (0=>1) The velocity stored in the 'SU' table will be recalculated to refer to the reference pixel. (2): Only for 'CALC' option: <= 0 => use latest VLA values (1999.2) or, for 1934-638, the ATCA value of 30Jul94. 1 => use Baars values or old ATCA/PKS values for 1934-638 2 => use mid-1990s VLA determined values (1995.2) or, for 1934-638, the ATCA value of 30Jul94. >= 3 => use oldest VLA determined values (1990) or, for 1934-638, the ATCA value of 30Jul94. ---------------------------------------------------------------- SETJY: Enter Source Flux Density and Calcode into the SU Table. Other source parameters may also be entered. RELATED PROGRAMS: CALIB PURPOSE The flux density scale of radio interferometers is often determined by observations of radio sources of known brightness. For interferometer observations, it is important that the standard sources used for this purpose be relatively compact. This is often at odds however with the requirement that the sources have very low variability over long timescales. For calibration of observations with the VLA, the radio sources 3C48, 3C286 and 3C147 are often used. In the southern hemisphere 1934-638 may also be used for this purpose. The standard reference for the flux density of bright radio sources is the paper by Baars, Genzel, Pauliny-Toth, Witzel 1977, Astron., Astrop. volume 61, page 99. The flux density of the standard sources can be modelled as a polynomial expansion over frequency. Polynomial coefficients have also been derived independently by R. Perley and G. Taylor as part of a long-term program to monitor the standard flux density calibrators at the VLA. These flux densities have been tied to 3C295 as it is believed that the bulk of the emission from 3C295 should remain constant over a timsecale of thousands of years. SETJY will calculate the expected flux density of the standard calibrators using either the Baars etal. coefficients or those derived from the VLA observations in 1990, 1995.2, or 1999.2. This option is selected by setting OPCODE to 'CALC'. The coefficient set to be used is selected using APARM(2), with the default giving the 1999.2 values. ** NOTE 1: As of the end of 2000, there still is uncertainty in the absolute VLA flux scale at 43 GHz, with the planets and NGC 7027 giving results that are discrepant by roughly 10%. For further information, consult the VLA Observational Status Summary, available via the VLA web site at http://www.aoc.nrao.edu/vla. ** NOTE 2: It was discovered several years ago that the existing 1990 VLA coefficients were rounded incorrectly in SETJY, introducing a positive bias of approximately 0.5%, 0.9%, 1.2%, 1.4% and 2.0% at P, L, C, X and U bands respectively for 3C286. The effect for other sources is less significant. This error affected AIPS versions up to and including 15JAN96. The 1990 coefficients implemented in subsequent versions have been corrected to remove the rounding error. For more detailed information regarding the variability of the standard flux density calibrators at the VLA the user is referred to the VLA calibrator manual which is available on the WWW at http://www.nrao.edu/doc/vla/html/calib.shtml. The source 1934-638 is the primary calibrator for the ATCA (Australia Telescope Compact Array). The flux density scale for 1934-638 was re-determined by John Reynolds (jreynold@atnf.csiro.au, 30/jul/94) and implemented in SETJY as the default on 30 August 1994. Changes in the flux density scale are significant at all frequencies. The old scale can be obtained with OPTYPE='CALC' by setting APARM(2)=1 Frequency New - Old (MHz) (%) --------------------------------- 408 -1.9 843 -3.5 1380 -7.9 1413 -8.1 1612 -9.3 1660 -9.5 1665 -9.5 2295 -11.4 2378 -11.5 4800 -7.9 4835 -7.8 4850 -7.8 8415 +8.5 8420 +8.5 8640 +9.8 The SETJY output in the SU table can be viewed with the tasks LISTR or PRTAB. ----------------------------------------------------------------