; SETJY ;--------------------------------------------------------------- ;! Task to enter source info into source (SU) table. ;# TASK CALIBRATION ;----------------------------------------------------------------------- ;; Copyright (C) 1995-1996, 2000, 2004-2005, 2007-2008, 2010-2012 ;; 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) (at 1 GHz if OPTYP='SPEC) SPECINDX -5.0 5.0 Spectral index SPECURVE Spectral index curvature OPTYPE ' ' => use other adverbs for required operation 'SPEC' => as ' ' but ZEROSP is at 1 GHz not freq of BIF 'CALC' => determine 3C286/3C48/1934 fluxes from standard formulae 'VCAL' set velocity of ref channel '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 best VLA values (2013/2010) 1 => use best VLA values (2010) = default before 13-Oct-2012 2 => use VLA 1999.2 values = default before 2/15/10 in SETJY 3 => use VLA 1995.2 values 4 => use oldest VLA values (1990) 5 => use Baars values (any) for 1934-638, the ATCA value of 30Jul94. (3): Only for 'CALC' option: multiply the calculated fluxes by APARM(3) with 0 -> 1 (4): Only for 'CALC' option: Use channel APARM(4)'s frequency for flux 0 -> center ---------------------------------------------------------------- SETJY Task: SETJY enters source information into the source (SU) table. If a model for the source is available, it should tell you. These models may be read with CALRD. CALIB scales the models to the total flux in the SU table, so this must be set for the actual observing frequency with SETJY even when models are used. CALIB now uses the "V polarization" flux when calibrating RR (= I + V) and LL (= I - V) correlators. This may be used for instruments with circular polarization if the calibrator is circularly polarized (not usually significant). It may also be used with equatorially mounted instruments having linearly polarized feeds. Such feeds do not rotate with parallactic angle and so have XX = I-Q and YY = I+Q. To calibrate these instruments, relabel the Stokes from (-5 to -8) to (-1 to -4) and put minus the Q flux into the V position (ZEROSP(4)). Some users have models for sources other than those provided with AIPS. To use such a model, it is recommended that you first run SETJY to set some total flux including spectral index and curvature in the SU table. Then the model will be scaled to that flux and GETJY may be used to adjust that scale after CALIB. If you do not set a non-zero flux for such calibrators, CALIB will use the flux contained in the model but GETJY will assume 1.0 and the result after GETJY will be erroneous. 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. This option is ignored if all 4 values are zero or if OPTYPE is 'CALC', 'VCAL', 'REJY', or 'RESE'. It is used otherwise to set the fluxes of all 4 polarizations. If ZEROSP(1) < 0, then the I polarization flux is not altered. This allows you to CALC the I flux and set the Q, U, and V fluxes. Note, if SPECINDX is not zero, then ZEROSP values are taken to be the values at 1 GHz (OPTYPE='SPEC') or at the frequency of BIF (OPTYPE not 'SPEC'). SPECINDX...Spectral index; 0 -> no spectral index of curvature. SPECURVE...Spectral curvature. The net flux of the source is then log (flux) = log (ZEROSP(i)) + SPECINDX * log (f) + SPECURVE(1) * [log(f)]^2 + SPECURVE(2) * [log(f)]^3 + SPECURVE(3) * [log(f)]^4 where all logarithms are base 10, f is the frequency in GHz, and flux is the source flux at frequency f. OPTYPE.....' ' => use ZEROSP values for the source flux densities at the frequency of BIF and SYSVEL for source velocity. 'SPEC' => as ' ' except that ZEROSP is interpreted as the fluxes at 1 GHz, the standard fiducial frequency. '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). ZEROSP is ignored. 'VCAL' => compute the velocity of the first observation in the data set for each of the requested sources and store it in the SU table. ZEROSP, SYSVEL and APARM(1) are ignored. RESTFREQ must be set in advance for each IF or specified by RESTFREQ. 'REJY' => reset source flux densities to zero for source(s) specified. ZEROSP is ignored. 'REVL' => reset velocity to zero for source(s) specified. 'RESE' => do both 'REJY' and 'REVL' operations. *********** WARNING: the following adverbs are used on all OPTYPEs *********** except as noted, but ' ' and 0.0 are not used to change *********** things. 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 (Perley-Butler 2013) or, for 1934-638, the ATCA value of 30Jul94. new values only for 3C286 and 3C295 (Begins 13-Oct-2012 as the default.) 1 => use latest VLA values (Perley-Butler 2010) or, for 1934-638, the ATCA value of 30Jul94. 2 => use VLA values from 1999.2 (available as the default in SETJY until from 22 Dec 2000 to 15 Feb 2010) 3 => use mid-1990s VLA determined values (1995.2) or, for 1934-638, the ATCA value of 30Jul94. 4 => use oldest VLA determined values (1990) or, for 1934-638, the ATCA value of 30Jul94. 5 => use Baars values or old ATCA/PKS values for 1934-638 (3): Only for 'CALC' option: You may wish to reduce the "official" flux computed from the VLA measurements to account for resolution effects. If 0 < APARM(3) <= 2.0, the computed flux is multipled by APARM(3). Use the model images instead! (4): Only for 'CALC' option: The spectral index computation requires a particular frequency to be used for the flux of each IF. The frequency used is the one for channel APARM(4) adjusted for each IF. 0 -> center of IF. Note that when say 1/2 of the IF is flagged for RFI, you can run SETJY for that IF only selecting a more central channel amongst those remaining. ---------------------------------------------------------------- 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 2010 values. The 2010 values are believed to be the best so far determined and 3C48, 3C147, 3C286, and 3C196 are believed to be essentially constant over time. The 2010 values in log units are Source log(f 1GHz) SPECINDX SPECURVE(1) SPECURVE(2) SPECURVE(3) 3C48 1.3197 -0.7253 -0.2023 0.0540 0.0 3C147 1.4428 -0.6300 -0.3142 0.1032 0.0 3C138 1.0053 -0.4384 -0.1855 0.0511 0.0 3C286 1.2361 -0.4127 -0.1864 0.0294 0.0 3C295 1.4605 -0.7043 -0.3951 0.0815 0.0 The numbers for 1934-638 (Reynolds, 02/Jul/94) are old and on a different scale entirely (1 MHz) and so are not given here. ***** WARNING - 3C48, 3C147, and especially 3C138 have not been stable in flux in recent years. 3C138 has doubled in flux at Q band in the past few years! Use these sources with great caution. ************* ** 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.vla.nrao.edu/ ** 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. If there are changes between the model being used and the previous of more than 3% the previous model will also be printed (although the current one is stored with the data). 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. There are now models of some calibrator sources shipped with AIPS. These models are read in with the task CALRD. The verb CALDIR will tell you what models are available. They cover the full range of VLA bands from L to Q. New models will be developed for the EVLA. Note, to use these as calibrators, you must enter a total flux in the source table with SETJY or GETJY which is correct for your observing frequency. Then CALIB will scale the flux in these models to that total flux. These models are in J2000 coordinates. If your data are in B1950, either change the uv data to J2000 with UVFIX or change the images to B1950 with EPOSWTCH. ----------------------------------------------------------------